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VulnerabilityPublished Updated

CVE-2025-39736: Linux kernel · mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f249d32bb54876b4b6c3ae071af8ddca77af390b : update Linux kernel when convenient.

Data as of 5 Nov 2026, 21:48 UTC

Severity
Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-05.

Patch
Available – fixed in f249d32bb54876b4b6c3ae071af8ddca77af390b, c7b6ea0ede687e7460e593c5ea478f50aa41682a, a0854de00ce2ee27edf39037e7836ad580eb3350 +6

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 Sep 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ c5665868183fec689dbab9fb8505188b2c4f0757, < f249d32bb54876b4b6c3ae071af8ddca77af390b
Fixed in
  • f249d32bb54876b4b6c3ae071af8ddca77af390b
LinuxLinuxAffected
  • ≥ c5665868183fec689dbab9fb8505188b2c4f0757, < c7b6ea0ede687e7460e593c5ea478f50aa41682a
Fixed in
  • c7b6ea0ede687e7460e593c5ea478f50aa41682a
LinuxLinuxAffected
  • ≥ c5665868183fec689dbab9fb8505188b2c4f0757, < a0854de00ce2ee27edf39037e7836ad580eb3350
Fixed in
  • a0854de00ce2ee27edf39037e7836ad580eb3350
LinuxLinuxAffected
  • ≥ c5665868183fec689dbab9fb8505188b2c4f0757, < a181b228b37a6a5625dad2bb4265bb7abb673e9f
Fixed in
  • a181b228b37a6a5625dad2bb4265bb7abb673e9f
LinuxLinuxAffected
  • ≥ c5665868183fec689dbab9fb8505188b2c4f0757, < 62879faa8efe8d8a9c7bf7606ee9c068012d7dac
Fixed in
  • 62879faa8efe8d8a9c7bf7606ee9c068012d7dac
LinuxLinuxAffected
  • ≥ c5665868183fec689dbab9fb8505188b2c4f0757, < 47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2
Fixed in
  • 47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2

AI-suggested

A fix is available and has been applied in the Linux kernel source. Systems running the affected version (=5.4) should update to a fixed kernel version containing the commit that moves pr_warn_once() outside the kmemleak_lock critical section. No additional mitigation is required once patched.

Description

A deadlock vulnerability in the Linux kernel's kmemleak subsystem occurs when pr_warn_once() is called while holding kmemleak_lock, causing lock inversion with the netconsole subsystem. This deadlock arises because pr_warn_once() triggers netpoll, which eventually attempts to reacquire kmemleak_lock. The issue is fixed by moving the pr_warn_once() call outside the kmemleak_lock critical section.

References

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