CyberSecBulletin
CVE-2026-23413NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-23413 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions a73d95b57bf9faebdfed591bcb7ed9292062a84c, 37bef86e5428d59f70a4da82b80f9a8f252fecbe, 4c9af67f99aa3e51b522c54968ab3ac8272be41c as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.16% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to a73d95b57bf9faebdfed591bcb7ed9292062a84c or 37bef86e5428d59f70a4da82b80f9a8f252fecbe or 4c9af67f99aa3e51b522c54968ab3ac8272be41c or 0509b762bc5e8ea7b8391130730c6d8502fc6e69, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.130 or 6.10 or 6.12.78 or 6.18.20, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux230bb13650b0f186f540500fd5f5f7096a822a2a up to, but not including, a73d95b57bf9faebdfed591bcb7ed9292062a84c; 1cb6f0bae50441f4b4b32a28315853b279c7404e up to, but not including, 37bef86e5428d59f70a4da82b80f9a8f252fecbe; 1cb6f0bae50441f4b4b32a28315853b279c7404e up to, but not including, 4c9af67f99aa3e51b522c54968ab3ac8272be41c; 1cb6f0bae50441f4b4b32a28315853b279c7404e up to, but not including, 0509b762bc5e8ea7b8391130730c6d8502fc6e69; 1cb6f0bae50441f4b4b32a28315853b279c7404e up to, but not including, a0671125d4f55e1e98d9bde8a0b671941987e208; f61ecf1bd5b562ebfd7d430ccb31619857e80857; 6.6.41 up to, but not including, 6.6.130; 6.9.10 up to, but not including, 6.10; and 1 more rangesa73d95b57bf9faebdfed591bcb7ed9292062a84c, 37bef86e5428d59f70a4da82b80f9a8f252fecbe, 4c9af67f99aa3e51b522c54968ab3ac8272be41c, 0509b762bc5e8ea7b8391130730c6d8502fc6e69, a0671125d4f55e1e98d9bde8a0b671941987e208, 6.6.130
LinuxLinux Kernel6.6.41 up to, but not including, 6.6.130; 6.9.10 up to, but not including, 6.10; 6.10.1 up to, but not including, 6.12.78; 6.13 up to, but not including, 6.18.20; 6.19 up to, but not including, 6.19.10; 6.10; 7.06.6.130, 6.10, 6.12.78, 6.18.20, 6.19.10

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: clsact: Fix use-after-free in init/destroy rollback asymmetry Fix a use-after-free in the clsact qdisc upon init/destroy rollback asymmetry. The latter is achieved by first fully initializing a clsact instance, and then in a second step having a replacement failure for the new clsact qdisc instance. clsact_init() initializes ingress first and then takes care of the egress part. This can fail midway, for example, via tcf_block_get_ext(). Upon failure, the kernel will trigger the clsact_destroy() callback. Commit 1cb6f0bae504 ("bpf: Fix too early release of tcx_entry") details the way how the transition is happening. If tcf_block_get_ext on the q->ingress_block ends up failing, we took the tcx_miniq_inc reference count on the ingress side, but not yet on the egress side. clsact_destroy() tests whether the {ingress,egress}_entry was non-NULL. However, even in midway failure on the replacement, both are in fact non-NULL with a valid egress_entry from the previous clsact instance. What we really need to test for is whether the qdisc instance-specific ingress or egress side previously got initialized. This adds a small helper for checking the miniq initialization called mini_qdisc_pair_inited, and utilizes that upon clsact_destroy() in order to fix the use-after-free scenario. Convert the ingress_destroy() side as well so both are consistent to each other.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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