CVE-2025-39977: Linux kernel · futex: Prevent use-after-free during requeue-PI
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 7.8 High · fixed in d824b2dbdcfe3c390278dd9652ea526168ef6850 : patch Linux kernel soon.
Data as of 10 Nov 2026, 14:47 UTC
Thin evidence
One scorer or none| CNA (Linux) | CVSS 3.1 | 7.8 |
|---|
- 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
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-10-15.
- Patch
- Available – fixed in d824b2dbdcfe3c390278dd9652ea526168ef6850, cb5d19a61274b51b49601214a87af573b43d60fa, b549113738e8c751b613118032a724b772aa83f2 +2
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 15 Oct 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 10 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– |
AI-suggested
A fix for this vulnerability has been implemented and is available in the Linux kernel. Users and administrators should update to the fixed kernel versions identified by the commits d824b2dbdcfe3c390278dd9652ea526168ef6850, cb5d19a61274b51b49601214a87af573b43d60fa, b549113738e8c751b613118032a724b772aa83f2, a170b9c0dde83312b8b58ccc91509c7c15711641, and 348736955ed6ca6e99ca24b93b1d3fbfe352c181. No additional mitigation steps are indicated beyond applying the official patch.
Description
CVE-2025-39977 is a high-severity use-after-free vulnerability in the Linux kernel's futex subsystem affecting version 5.15. It arises from a race condition during the requeue-PI operation where synchronization is improperly handled, potentially leading to use of freed memory. The flaw was triggered by syzbot and involves the futex_q structure's task pointer being accessed unsafely during state updates. The issue is resolved by ensuring futex_q::task is read before updating the requeue state, leveraging existing spinlock and RCU protections to maintain task_struct validity during wakeup.
References
- git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa (opens in a new tab)
- git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181 (opens in a new tab)
- git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641 (opens in a new tab)
- git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850 (opens in a new tab)
- git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2 (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-082556.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)