CyberSecBulletin
CVE-2026-23391NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-23391 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 55445134d42b84cb0a272e42c98d233ca65eca83, cc57506dd66555899560b9c0f24e813f034e12ec, d2d0bae0c9a2a17b6990a2966f5cdce0813d6256 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 0.13% 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 55445134d42b84cb0a272e42c98d233ca65eca83 or cc57506dd66555899560b9c0f24e813f034e12ec or d2d0bae0c9a2a17b6990a2966f5cdce0813d6256 or 63b8097cea1923fe82cd598068d0796da8c015ec, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.167 or 6.6.130, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, 55445134d42b84cb0a272e42c98d233ca65eca83; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, cc57506dd66555899560b9c0f24e813f034e12ec; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, d2d0bae0c9a2a17b6990a2966f5cdce0813d6256; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, 63b8097cea1923fe82cd598068d0796da8c015ec; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, 19a230dec6bb8928e3f96387f9085cf2c79bcef9; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, cb549925875fa06dd155e49db4ac2c5044c30f9c; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, 777d02efe3d630cca4c1b63962cec17c57711325; 24de58f465165298aaa8f286b2592f0163706cfe up to, but not including, f62a218a946b19bb59abdd5361da85fa4606b96b; and 1 more ranges55445134d42b84cb0a272e42c98d233ca65eca83, cc57506dd66555899560b9c0f24e813f034e12ec, d2d0bae0c9a2a17b6990a2966f5cdce0813d6256, 63b8097cea1923fe82cd598068d0796da8c015ec, 19a230dec6bb8928e3f96387f9085cf2c79bcef9, cb549925875fa06dd155e49db4ac2c5044c30f9c
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)V3.1.6 and later; V3.1.5 and later; V3.1.7 and laterNot stated
LinuxLinux Kernel3.4.1 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.167; 6.2 up to, but not including, 6.6.130; 6.7 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; 3.4; and 1 more ranges5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.20

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 CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_CT: drop pending enqueued packets on template removal Templates refer to objects that can go away while packets are sitting in nfqueue refer to: - helper, this can be an issue on module removal. - timeout policy, nfnetlink_cttimeout might remove it. The use of templates with zone and event cache filter are safe, since this just copies values. Flush these enqueued packets in case the template rule gets removed.

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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