CVE-2026-31555futex: Clear stale exiting pointer in futex_lock_pi() retry path
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before 33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before e7824ec168d2ac883a213cd1f4d6cc0816002a85; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before 5e8e06bf8909e79b4acd950cf578cfc2f10bbefa; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before de7c0c04ad868f2cee6671b11c0a6d20421af1da; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before 7475dfad10a05a5bfadebf5f2499bd61b19ed293; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before 92e47ad03e03dbb5515bdf06444bf6b1e147310d; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before 71112e62807d1925dc3ae6188b11f8cfc85aec23; from 3ef240eaff36b8119ac9e2ea17cbf41179c930ba before 210d36d892de5195e6766c45519dfb1e65f3eb83; and 10 more ranges | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 4.4.255 before 4.5; from 4.9.255 before 4.10; from 4.14.158 before 4.15; from 4.19.172 before 4.20; from 5.4.1 before 5.5; from 5.5.1 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.168; and 12 more ranges | NVD |
References
- https://git.kernel.org/stable/c/33095ae3bdde5e5c264d7e88a2f3e7703a26c7aapatch
- https://git.kernel.org/stable/c/e7824ec168d2ac883a213cd1f4d6cc0816002a85patch
- https://git.kernel.org/stable/c/5e8e06bf8909e79b4acd950cf578cfc2f10bbefapatch
- https://git.kernel.org/stable/c/de7c0c04ad868f2cee6671b11c0a6d20421af1dapatch
- https://git.kernel.org/stable/c/7475dfad10a05a5bfadebf5f2499bd61b19ed293patch
- https://git.kernel.org/stable/c/92e47ad03e03dbb5515bdf06444bf6b1e147310dpatch
- https://git.kernel.org/stable/c/71112e62807d1925dc3ae6188b11f8cfc85aec23patch
- https://git.kernel.org/stable/c/210d36d892de5195e6766c45519dfb1e65f3eb83patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.