CVE-2026-23074: Linux kernel · Use After Free
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 3.13.0-212.263 : patch Linux kernel soon.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 3.13.0-212.263, 4.4.0-1153.159, 4.15.0-1199.214~14.04.1 +113
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 4 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linuxpkg:deb/ubuntu/linux@6.17.0-20.20?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws@6.17.0-1010.10?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure@6.17.0-1011.11?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde@6.17.0-1017.17?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp@6.17.0-1010.10?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle@6.17.0-1010.10?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: Enforce that teql can only be used as root qdisc Design intent of teql is that it is only supposed to be used as root qdisc. We need to check for that constraint. Although not important, I will describe the scenario that unearthed this issue for the curious. GangMin Kim <km.kim1503@gmail.com> managed to concot a scenario as follows: ROOT qdisc 1:0 (QFQ) ├── class 1:1 (weight=15, lmax=16384) netem with delay 6.4s └── class 1:2 (weight=1, lmax=1514) teql GangMin sends a packet which is enqueued to 1:1 (netem). Any invocation of dequeue by QFQ from this class will not return a packet until after 6.4s. In the meantime, a second packet is sent and it lands on 1:2. teql's enqueue will return success and this will activate class 1:2. Main issue is that teql only updates the parent visible qlen (sch->q.qlen) at dequeue. Since QFQ will only call dequeue if peek succeeds (and teql's peek always returns NULL), dequeue will never be called and thus the qlen will remain as 0. With that in mind, when GangMin updates 1:2's lmax value, the qfq_change_class calls qfq_deact_rm_from_agg. Since the child qdisc's qlen was not incremented, qfq fails to deactivate the class, but still frees its pointers from the aggregate. So when the first packet is rescheduled after 6.4 seconds (netem's delay), a dangling pointer is accessed causing GangMin's causing a UAF.
References
- ubuntu.com/security/CVE-2026-23074 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23074 (opens in a new tab)
- git.kernel.org/linus/50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b (opens in a new tab)
- git.kernel.org/stable/c/0686bedfed34155520f3f735cbf3210cb9044380 (opens in a new tab)
- git.kernel.org/stable/c/16ed73c1282d376b956bff23e5139add061767ba (opens in a new tab)
- git.kernel.org/stable/c/4c7e8aa71c9232cba84c289b4b56cba80b280841 (opens in a new tab)
- git.kernel.org/stable/c/50da4b9d07a7a463e2cfb738f3ad4cff6b2c9c3b (opens in a new tab)
- ubuntu.com/security/notices/USN-8142-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8143-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8145-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8149-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8143-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8145-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8145-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8148-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8152-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8159-1 (opens in a new tab)
- suse.com/support/security/rating/ (opens in a new tab)
- ftp.suse.com/pub/projects/security/csaf/suse-su-2026_21004-1.json (opens in a new tab)
- suse.com/support/update/announcement/2026/suse-su-202621004-1/ (opens in a new tab)
- lists.suse.com/pipermail/sle-updates/2026-April/045402.html (opens in a new tab)
- bugzilla.suse.com/1258051 (opens in a new tab)
- bugzilla.suse.com/1258183 (opens in a new tab)
- bugzilla.suse.com/1258784 (opens in a new tab)
- suse.com/security/cve/CVE-2026-23074/ (opens in a new tab)
- suse.com/security/cve/CVE-2026-23111/ (opens in a new tab)
- suse.com/security/cve/CVE-2026-23209/ (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-23074 (opens in a new tab)
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23074.json (opens in a new tab)
- git.kernel.org/stable/c/dad49a67c2d817bfec98e6e45121b351e3a0202c (opens in a new tab)
- git.kernel.org/stable/c/ae810e6a8ac4fe25042e6825d2a401207a2e41fb (opens in a new tab)
- git.kernel.org/stable/c/73d970ff0eddd874a84c953387c7f4464b705fc6 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2436791 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2026-23074 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3810 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3685 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3634 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3388 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3360 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3277 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3268 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3110 (opens in a new tab)
- access.redhat.com/errata/RHSA-2026:3083 (opens in a new tab)