CyberSecBulletin
CVE-2026-23270NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-23270 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 bc4e5bb529823a09f02dbe96169de679a9db26e0, fb3c380a54e33d1fd272cc342faa906d787d7ef1, 5a110ddcc99bda77a28598b3555fe009eaab3828 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 0.15% 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 bc4e5bb529823a09f02dbe96169de679a9db26e0 or fb3c380a54e33d1fd272cc342faa906d787d7ef1 or 5a110ddcc99bda77a28598b3555fe009eaab3828 or 524ce8b4ea8f64900b6c52b6a28df74f6bc0801e, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.203 or 6.1.167 or 6.6.130 or 6.8, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux172ba7d46c202e679f3ccb10264c67416aaeb1c4 up to, but not including, bc4e5bb529823a09f02dbe96169de679a9db26e0; 0b5b831122fc3789fff75be433ba3e4dd7b779d4 up to, but not including, fb3c380a54e33d1fd272cc342faa906d787d7ef1; 73f7da5fd124f2cda9161e2e46114915e6e82e97 up to, but not including, 5a110ddcc99bda77a28598b3555fe009eaab3828; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, 524ce8b4ea8f64900b6c52b6a28df74f6bc0801e; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, 380ad8b7c65ea7aa10ef2258297079ed5ac1f5b6; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, 9deda0fcda5c1f388c5e279541850b71a2ccfcf4; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, 11cb63b0d1a0685e0831ae3c77223e002ef18189; f5346df0591d10bc948761ca854b1fae6d2ef441; and 5 more rangesbc4e5bb529823a09f02dbe96169de679a9db26e0, fb3c380a54e33d1fd272cc342faa906d787d7ef1, 5a110ddcc99bda77a28598b3555fe009eaab3828, 524ce8b4ea8f64900b6c52b6a28df74f6bc0801e, 380ad8b7c65ea7aa10ef2258297079ed5ac1f5b6, 9deda0fcda5c1f388c5e279541850b71a2ccfcf4
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 Kernel5.15.148 up to, but not including, 5.15.203; 6.1.75 up to, but not including, 6.1.167; 6.6.14 up to, but not including, 6.6.130; 6.7.2 up to, but not including, 6.8; 6.8 up to, but not including, 6.12.77; 6.13 up to, but not including, 6.18.18; 6.19 up to, but not including, 6.19.8; 7.05.15.203, 6.1.167, 6.6.130, 6.8, 6.12.77, 6.18.18

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: net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks As Paolo said earlier [1]: "Since the blamed commit below, classify can return TC_ACT_CONSUMED while the current skb being held by the defragmentation engine. As reported by GangMin Kim, if such packet is that may cause a UaF when the defrag engine later on tries to tuch again such packet." act_ct was never meant to be used in the egress path, however some users are attaching it to egress today [2]. Attempting to reach a middle ground, we noticed that, while most qdiscs are not handling TC_ACT_CONSUMED, clsact/ingress qdiscs are. With that in mind, we address the issue by only allowing act_ct to bind to clsact/ingress qdiscs and shared blocks. That way it's still possible to attach act_ct to egress (albeit only with clsact). [1] https://lore.kernel.org/netdev/674b8cbfc385c6f37fb29a1de08d8fe5c2b0fbee.1771321118.git.pabeni@redhat.com/ [2] https://lore.kernel.org/netdev/[email protected]/

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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