CyberSecBulletin
CVE-2026-43437NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-43437 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 9baee36e8c5443411c4629afabafaff8a46a23fd, f2cb2e0d27fb925c73a78f0ce7d6dbf68d3747c1, fc71f888994569f87d5bee20b1ac6c9c1e3a7a79 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 9baee36e8c5443411c4629afabafaff8a46a23fd or f2cb2e0d27fb925c73a78f0ce7d6dbf68d3747c1 or fc71f888994569f87d5bee20b1ac6c9c1e3a7a79 or 629cf09464cf98670996ea5c191dc9743e6f3f00, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.253 or 6.1.167 or 6.6.130 or 6.12.78, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxf2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, 9baee36e8c5443411c4629afabafaff8a46a23fd; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, f2cb2e0d27fb925c73a78f0ce7d6dbf68d3747c1; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, fc71f888994569f87d5bee20b1ac6c9c1e3a7a79; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, 629cf09464cf98670996ea5c191dc9743e6f3f00; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, ae8f8d30d334bad5b1b3cdb1eb8a0b771f55e432; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, 4a758e9a1f5ed722f83c4dd35f867fe811553bcb; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, c2f64e05a0587a83ec42dbd6b7a7ded79b2ff694; f2b3614cefb61ee6046a0aaee503ee37f227d310 up to, but not including, 9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6; and 1 more ranges9baee36e8c5443411c4629afabafaff8a46a23fd, f2cb2e0d27fb925c73a78f0ce7d6dbf68d3747c1, fc71f888994569f87d5bee20b1ac6c9c1e3a7a79, 629cf09464cf98670996ea5c191dc9743e6f3f00, ae8f8d30d334bad5b1b3cdb1eb8a0b771f55e432, 4a758e9a1f5ed722f83c4dd35f867fe811553bcb
LinuxLinux Kernel3.0 up to, but not including, 5.10.253; 5.11 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, 6.18.19; 6.19 up to, but not including, 6.19.9; 7.05.10.253, 6.1.167, 6.6.130, 6.12.78, 6.18.19, 6.19.9

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: ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain() In the drain loop, the local variable 'runtime' is reassigned to a linked stream's runtime (runtime = s->runtime at line 2157). After releasing the stream lock at line 2169, the code accesses runtime->no_period_wakeup, runtime->rate, and runtime->buffer_size (lines 2170-2178) — all referencing the linked stream's runtime without any lock or refcount protecting its lifetime. A concurrent close() on the linked stream's fd triggers snd_pcm_release_substream() → snd_pcm_drop() → pcm_release_private() → snd_pcm_unlink() → snd_pcm_detach_substream() → kfree(runtime). No synchronization prevents kfree(runtime) from completing while the drain path dereferences the stale pointer. Fix by caching the needed runtime fields (no_period_wakeup, rate, buffer_size) into local variables while still holding the stream lock, and using the cached values after the lock is released.

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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