CVE-2026-31555
Description
In the Linux kernel, the following vulnerability has been resolved: futex: Clear stale exiting pointer in futex_lock_pi() retry path Fuzzying/stressing futexes triggered: WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524 When futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY and stores a refcounted task pointer in 'exiting'. After wait_for_owner_exiting() consumes that reference, the local pointer is never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a different error, the bogus pointer is passed to wait_for_owner_exiting(). CPU0 CPU1 CPU2 futex_lock_pi(uaddr) // acquires the PI futex exit() futex_cleanup_begin() futex_state = EXITING; futex_lock_pi(uaddr) futex_lock_pi_atomic() attach_to_pi_owner() // observes EXITING *exiting = owner; // takes ref return -EBUSY wait_for_owner_exiting(-EBUSY, owner) put_task_struct(); // drops ref // exiting still points to owner goto retry; futex_lock_pi_atomic() lock_pi_update_atomic() cmpxchg(uaddr) *uaddr ^= WAITERS // whatever // value changed return -EAGAIN; wait_for_owner_exiting(-EAGAIN, exiting) // stale WARN_ON_ONCE(exiting) Fix this by resetting upon retry, essentially aligning it with requeue_pi.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
Linux kernel Affected 3 releases
| Version | Status | Fixed in |
|---|---|---|
| 7.0 | Affected | — |
| 5.5 | Affected | — |
| — | Affected | 4.5 |
SUSE Affected 1 release
| Version | Status | Fixed in |
|---|---|---|
| — | Affected | — |
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 6.12.85-1 |
| sid | Fixed | 6.19.11-1 |
| forky | Fixed | 6.19.11-1 |
| bullseye | Fixed | 6.1.170-1~deb11u1 |
| bookworm | Fixed | 6.1.170-1 |
Application impact
| Vendor | Product | Versions | Fixed |
|---|---|---|---|
| gcp | | |
References
- https://git.kernel.org/stable/c/210d36d892de5195e6766c45519dfb1e65f3eb83
- https://git.kernel.org/stable/c/33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa
- https://git.kernel.org/stable/c/5e8e06bf8909e79b4acd950cf578cfc2f10bbefa
- https://git.kernel.org/stable/c/71112e62807d1925dc3ae6188b11f8cfc85aec23
- https://git.kernel.org/stable/c/7475dfad10a05a5bfadebf5f2499bd61b19ed293
- https://git.kernel.org/stable/c/92e47ad03e03dbb5515bdf06444bf6b1e147310d
- https://git.kernel.org/stable/c/de7c0c04ad868f2cee6671b11c0a6d20421af1da
- https://git.kernel.org/stable/c/e7824ec168d2ac883a213cd1f4d6cc0816002a85
- https://www.suse.com/security/cve/CVE-2026-31555.html
- https://security-tracker.debian.org/tracker/CVE-2026-31555
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.