CVE-2026-74658: futex: Prevent robust futex exit race some more
futex: Prevent robust futex exit race some more
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.6.152.1-1 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Patch 3ca9595d9fb6 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Patch ca16d5bee598 - Operational
Apply the mainline follow-up that amends the futex robust wakeup/exit handling: the change described as 'futex: Prevent robust futex exit race some more' and the robust futex unlock support in commits 3ca9595d9fb6 and ca16d5bee598.
Event History
Frequently Asked Questions
Which systems are realistically exposed to this issue?
Systems running Linux workloads that use robust futexes and can have multiple tasks contending for the same futex are exposed. The failure affects waiters that can remain blocked indefinitely after a specific race.
What sequence is required for the race to cause an indefinite wait?
A robust futex unlock must clear the FUTEX_WAITERS state and wake one waiter, and that woken waiter must be killed before acquiring the futex or restoring FUTEX_WAITERS. Another task must then reacquire the futex through the uncontended fast path, allowing remaining waiters to sleep behind a free futex.
What is the practical impact if the race occurs?
Remaining futex waiters can sleep forever even though the futex is no longer held. This can cause affected application tasks to hang.
What can be done if the affected kernel cannot be updated immediately?
The provided data identifies the resolved stable-kernel changes in the listed references. No configuration-based workaround or reliable runtime detection method is provided.