CyberSecBulletin
CVE-2026-43499NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-43499 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 f3fa3424bceb128d2be4b3745506b22844b87db7, 838ce5cb5d93c3ab8b27e75bc6ad905a94b752fd, d8cce4773c2b23d819baf5abedc62f7b430e8745 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 5.37% chance of exploitation within 30 days, which is in the top 7.22% of all scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to f3fa3424bceb128d2be4b3745506b22844b87db7 or 838ce5cb5d93c3ab8b27e75bc6ad905a94b752fd or d8cce4773c2b23d819baf5abedc62f7b430e8745 or 8a1fc8d698ac5e5916e3082a0f74450d71f9611f, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.175 or 6.6.140 or 6.12.86 or 6.18.27, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, f3fa3424bceb128d2be4b3745506b22844b87db7; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, 838ce5cb5d93c3ab8b27e75bc6ad905a94b752fd; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, d8cce4773c2b23d819baf5abedc62f7b430e8745; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, 8a1fc8d698ac5e5916e3082a0f74450d71f9611f; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, 6d52dfcb2a5db86e346cf51f8fcf2071b8085166; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, 3fb7394a837740770f0d6b4b30567e60786a63f2; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, 88614876370aac8ad1050ad785a4c095ba17ac11; 8161239a8bcce9ad6b537c04a1fa3b5c68bae693 up to, but not including, 3bfdc63936dd4773109b7b8c280c0f3b5ae7d349; and 1 more rangesf3fa3424bceb128d2be4b3745506b22844b87db7, 838ce5cb5d93c3ab8b27e75bc6ad905a94b752fd, d8cce4773c2b23d819baf5abedc62f7b430e8745, 8a1fc8d698ac5e5916e3082a0f74450d71f9611f, 6d52dfcb2a5db86e346cf51f8fcf2071b8085166, 3fb7394a837740770f0d6b4b30567e60786a63f2
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)V3.1.6 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; V3.1.7 and laterNot stated
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)V3.1.6 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; V3.1.7 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; V3.1.7 and laterNot stated
LinuxLinux Kernel2.6.39 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.140; 6.7 up to, but not including, 6.12.86; 6.13 up to, but not including, 6.18.27; 6.19 up to, but not including, 7.0.46.1.175, 6.6.140, 6.12.86, 6.18.27, 7.0.4

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: rtmutex: Use waiter::task instead of current in remove_waiter() remove_waiter() is used by the slowlock paths, but it is also used for proxy-lock rollback in rt_mutex_start_proxy_lock() when invoked from futex_requeue(). In the latter case waiter::task is not current, but remove_waiter() operates on current for the dequeue operation. That results in several problems: 1) the rbtree dequeue happens without waiter::task::pi_lock being held 2) the waiter task's pi_blocked_on state is not cleared, which leaves a dangling pointer primed for UAF around. 3) rt_mutex_adjust_prio_chain() operates on the wrong top priority waiter task Use waiter::task instead of current in all related operations in remove_waiter() to cure those problems. [ tglx: Fixup rt_mutex_adjust_prio_chain(), add a comment and amend the changelog ]

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: poc, 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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