CVE-2026-52977: Linux kernel · futex: Prevent lockup in requeue-PI during signal/ timeout wakeup
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c : update Linux kernel when convenient.
Data as of 6 Nov 2026, 16:49 UTC
Rated by Threat Radar · 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, 2026-11-06.
- Patch
- Available – fixed in e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c, e3f95b1ba242e37093305812df7fdbe7288a43ac, bc7304f3ae20972d11db6e0b1b541c63feda5f05 +4
Exploitation evidence
Disclosed: evidence found.
CVE published 24 Jun 2026
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 6 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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Description
In the Linux kernel, the following vulnerability has been resolved: futex: Prevent lockup in requeue-PI during signal/ timeout wakeup During wait-requeue-pi (task A) and requeue-PI (task B) the following race can happen: Task A Task B futex_wait_requeue_pi() futex_setup_timer() futex_do_wait() futex_requeue() CLASS(hb, hb1)(&key1); CLASS(hb, hb2)(&key2); *timeout* futex_requeue_pi_wakeup_sync() requeue_state = Q_REQUEUE_PI_IGNORE *blocks on hb->lock* futex_proxy_trylock_atomic() futex_requeue_pi_prepare() Q_REQUEUE_PI_IGNORE => -EAGAIN double_unlock_hb(hb1, hb2) *retry* Task B acquires both hb locks and attempts to acquire the PI-lock of the top most waiter (task B). Task A is leaving early due to a signal/ timeout and started removing itself from the queue. It updates its requeue_state but can not remove it from the list because this requires the hb lock which is owned by task B. Usually task A is able to swoop the lock after task B unlocked it. However if task B is of higher priority then task A may not be able to wake up in time and acquire the lock before task B gets it again. Especially on a UP system where A is never scheduled. As a result task A blocks on the lock and task B busy loops, trying to make progress but live locks the system instead. Tragic. This can be fixed by removing the top most waiter from the list in this case. This allows task B to grab the next top waiter (if any) in the next iteration and make progress. Remove the top most waiter if futex_requeue_pi_prepare() fails. Let the waiter conditionally remove itself from the list in handle_early_requeue_pi_wakeup().
References
- git.kernel.org/stable/c/e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c (opens in a new tab)
- git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966 (opens in a new tab)
- git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac (opens in a new tab)
- git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf (opens in a new tab)
- git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c (opens in a new tab)
- git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0 (opens in a new tab)
- git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05 (opens in a new tab)