CVE-2025-39736: Linux kernel · mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in f249d32bb54876b4b6c3ae071af8ddca77af390b : update Linux kernel when convenient.
Data as of 5 Nov 2026, 21:48 UTC
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
Disclosed: evidence found.
CVE published 11 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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
- git.kernel.org/stable/c/c7b6ea0ede687e7460e593c5ea478f50aa41682a (opens in a new tab)
- git.kernel.org/stable/c/4b0151e1d468eb2667c37b7af99b3c075072d334 (opens in a new tab)
- git.kernel.org/stable/c/f249d32bb54876b4b6c3ae071af8ddca77af390b (opens in a new tab)
- git.kernel.org/stable/c/62879faa8efe8d8a9c7bf7606ee9c068012d7dac (opens in a new tab)
- git.kernel.org/stable/c/1da95d3d4b7b1d380ebd87b71a61e7e6aed3265d (opens in a new tab)
- git.kernel.org/stable/c/a0854de00ce2ee27edf39037e7836ad580eb3350 (opens in a new tab)
- git.kernel.org/stable/c/08f70be5e406ce47c822f2dd11c1170ca259605b (opens in a new tab)
- git.kernel.org/stable/c/a181b228b37a6a5625dad2bb4265bb7abb673e9f (opens in a new tab)
- git.kernel.org/stable/c/47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00008.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/10/msg00007.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-032379.html (opens in a new tab)