Medium [CVE-2026-52977] Prevent lockup in requeue-PI during signal/ timeout wakeup
This medium-severity Red Hat Linux advisory covers CVE-2026-52977 affecting Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 10, Red Hat package: kernel-rt.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Summary
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.
Is CVE-2026-52977 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-52977 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-52977?
Upgrade to a fixed release named by Red Hat:
- kernel-0:5.14.0-687.36.1.el9_8
- RHSA-2026:51035
Confirm against the vendor advisory before you patch.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 14 days ago·verify at source
- kernel-0:5.14.0-687.36.1.el9_8
- RHSA-2026:51035
Official advisory · high-confidence parse· fetched 14 days ago·verify at source
Mitigation
Upgrade to a fixed release: kernel-0:5.14.0-687.36.1.el9_8, RHSA-2026:51035. That is the remediation for this advisory.
The vendor advisory may list interim mitigations or workarounds not captured here. Review it before change work.
Official advisory · high-confidence parse· fetched 14 days ago·verify at source
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