{"cvss":5.5,"datePublished":"2026-04-24T15:16:29.837","dateUpdated":"2026-11-05T22:18:40.093","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Clear stale exiting pointer in futex_lock_pi() retry path\n\nFuzzying/stressing futexes triggered:\n\n    WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524\n\nWhen futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY\nand stores a refcounted task pointer in 'exiting'.\n\nAfter wait_for_owner_exiting() consumes that reference, the local pointer\nis never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a\ndifferent error, the bogus pointer is passed to wait_for_owner_exiting().\n\n  CPU0\t\t\t     CPU1\t\t       CPU2\n  futex_lock_pi(uaddr)\n  // acquires the PI futex\n  exit()\n    futex_cleanup_begin()\n      futex_state = EXITING;\n\t\t\t     futex_lock_pi(uaddr)\n\t\t\t       futex_lock_pi_atomic()\n\t\t\t\t attach_to_pi_owner()\n\t\t\t\t   // observes EXITING\n\t\t\t\t   *exiting = owner;  // takes ref\n\t\t\t\t   return -EBUSY\n\t\t\t       wait_for_owner_exiting(-EBUSY, owner)\n\t\t\t\t put_task_struct();   // drops ref\n\t\t\t       // exiting still points to owner\n\t\t\t       goto retry;\n\t\t\t       futex_lock_pi_atomic()\n\t\t\t\t lock_pi_update_atomic()\n\t\t\t\t   cmpxchg(uaddr)\n\t\t\t\t\t*uaddr ^= WAITERS // whatever\n\t\t\t\t   // value changed\n\t\t\t\t return -EAGAIN;\n\t\t\t       wait_for_owner_exiting(-EAGAIN, exiting) // stale\n\t\t\t\t WARN_ON_ONCE(exiting)\n\nFix this by resetting upon retry, essentially aligning it with requeue_pi.","id":"CVE-2026-31555","raw":{"affected":[{"affectedData":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["kernel/futex/pi.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"e7824ec168d2ac883a213cd1f4d6cc0816002a85","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"5e8e06bf8909e79b4acd950cf578cfc2f10bbefa","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"de7c0c04ad868f2cee6671b11c0a6d20421af1da","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"7475dfad10a05a5bfadebf5f2499bd61b19ed293","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"92e47ad03e03dbb5515bdf06444bf6b1e147310d","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"71112e62807d1925dc3ae6188b11f8cfc85aec23","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"lessThan":"210d36d892de5195e6766c45519dfb1e65f3eb83","status":"affected","version":"3ef240eaff36b8119ac9e2ea17cbf41179c930ba","versionType":"git"},{"status":"affected","version":"f2a9957e5c08b1b1caacd18a3dc4c0a1bdb7b463","versionType":"git"},{"status":"affected","version":"cf16e42709aa86aa3e37f3acc3d13d5715d90096","versionType":"git"},{"status":"affected","version":"61fa9f167caaa73d0a7c88f498eceeb12c6fa3db","versionType":"git"},{"status":"affected","version":"7874eee0130adf9bee28e8720bb5dd051089def3","versionType":"git"},{"status":"affected","version":"fc3b55ef2c840bb2746b2d8121a0788de84f7fac","versionType":"git"},{"lessThan":"4.5","status":"affected","version":"4.4.255","versionType":"semver"},{"lessThan":"4.10","status":"affected","version":"4.9.255","versionType":"semver"},{"lessThan":"4.15","status":"affected","version":"4.14.158","versionType":"semver"},{"lessThan":"4.20","status":"affected","version":"4.19.172","versionType":"semver"},{"lessThan":"5.5","status":"affected","version":"5.4.1","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["kernel/futex/pi.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.5"},{"lessThan":"5.5","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.253","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.203","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.168","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.131","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.80","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.21","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.11","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"affectedData":[{"defaultStatus":"unknown","product":"SIMATIC 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MFP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]}],"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"configurations":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"39A57944-7654-4465-9F2B-4DC1CB18ADFB","versionEndExcluding":"4.5","versionStartIncluding":"4.4.255","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"F932A542-7872-4F86-AD1E-00CCC240C25D","versionEndExcluding":"4.10","versionStartIncluding":"4.9.255","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"C62F59A2-9EFC-4E7F-B9E7-3DFF4E885406","versionEndExcluding":"4.15","versionStartIncluding":"4.14.158","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"235BE773-4E0B-4AD6-9314-D176A65C4B73","versionEndExcluding":"4.20","versionStartIncluding":"4.19.172","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"025DC0BA-08A8-4703-AE9F-7C3D8E346A45","versionEndExcluding":"5.5","versionStartIncluding":"5.4.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"45E871E1-B00E-4E88-83A3-60B38EAF2B8A","versionEndExcluding":"5.10.253","versionStartIncluding":"5.5.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"20DDB3E9-AABF-4107-ADB0-5362AA067045","versionEndExcluding":"5.15.203","versionStartIncluding":"5.11","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B","versionEndExcluding":"6.1.168","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"CE6ED4D4-0046-4573-BFA9-D64143B6A89F","versionEndExcluding":"6.6.131","versionStartIncluding":"6.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6","versionEndExcluding":"6.12.80","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"ED39847A-3B46-4729-B7CA-B2C30B9FA8FE","versionEndExcluding":"6.18.21","versionStartIncluding":"6.13","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","matchCriteriaId":"4CA2E747-A9EC-4518-9AA2-B4247FC748B7","versionEndExcluding":"6.19.11","versionStartIncluding":"6.19","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:5.5:-:*:*:*:*:*:*","matchCriteriaId":"EE98F46A-F7D9-4609-B6A0-882E7F0D378C","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*","matchCriteriaId":"F253B622-8837-4245-BCE5-A7BF8FC76A16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*","matchCriteriaId":"4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*","matchCriteriaId":"F666C8D8-6538-46D4-B318-87610DE64C34","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*","matchCriteriaId":"02259FDA-961B-47BC-AE7F-93D7EC6E90C2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*","matchCriteriaId":"58A9FEFF-C040-420D-8F0A-BFDAAA1DF258","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*","matchCriteriaId":"1D2315C0-D46F-4F85-9754-F9E5E11374A6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*","matchCriteriaId":"512EE3A8-A590-4501-9A94-5D4B268D6138","vulnerable":true}],"negate":false,"operator":"OR"}]}],"cveTags":[],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Clear stale exiting pointer in futex_lock_pi() retry path\n\nFuzzying/stressing futexes triggered:\n\n    WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524\n\nWhen futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY\nand stores a refcounted task pointer in 'exiting'.\n\nAfter wait_for_owner_exiting() consumes that reference, the local pointer\nis never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a\ndifferent error, the bogus pointer is passed to wait_for_owner_exiting().\n\n  CPU0\t\t\t     CPU1\t\t       CPU2\n  futex_lock_pi(uaddr)\n  // acquires the PI futex\n  exit()\n    futex_cleanup_begin()\n      futex_state = EXITING;\n\t\t\t     futex_lock_pi(uaddr)\n\t\t\t       futex_lock_pi_atomic()\n\t\t\t\t attach_to_pi_owner()\n\t\t\t\t   // observes EXITING\n\t\t\t\t   *exiting = owner;  // takes ref\n\t\t\t\t   return -EBUSY\n\t\t\t       wait_for_owner_exiting(-EBUSY, owner)\n\t\t\t\t put_task_struct();   // drops ref\n\t\t\t       // exiting still points to owner\n\t\t\t       goto retry;\n\t\t\t       futex_lock_pi_atomic()\n\t\t\t\t lock_pi_update_atomic()\n\t\t\t\t   cmpxchg(uaddr)\n\t\t\t\t\t*uaddr ^= WAITERS // whatever\n\t\t\t\t   // value changed\n\t\t\t\t return -EAGAIN;\n\t\t\t       wait_for_owner_exiting(-EAGAIN, exiting) // stale\n\t\t\t\t WARN_ON_ONCE(exiting)\n\nFix this by resetting upon retry, essentially aligning it with requeue_pi."}],"id":"CVE-2026-31555","lastModified":"2026-11-05T22:18:40.093","metrics":{"cvssMetricV31":[{"cvssData":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":5.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"exploitabilityScore":1.8,"impactScore":3.6,"source":"nvd@nist.gov","type":"Primary"}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"id":"CVE-2026-31555","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-11-05T21:38:41.447334Z","version":"2.0.3"}}]},"published":"2026-04-24T15:16:29.837","references":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/210d36d892de5195e6766c45519dfb1e65f3eb83"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/5e8e06bf8909e79b4acd950cf578cfc2f10bbefa"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/71112e62807d1925dc3ae6188b11f8cfc85aec23"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/7475dfad10a05a5bfadebf5f2499bd61b19ed293"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/92e47ad03e03dbb5515bdf06444bf6b1e147310d"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/de7c0c04ad868f2cee6671b11c0a6d20421af1da"},{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":["Patch"],"url":"https://git.kernel.org/stable/c/e7824ec168d2ac883a213cd1f4d6cc0816002a85"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html"},{"source":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}],"sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","vulnStatus":"Modified","weaknesses":[{"description":[{"lang":"en","value":"NVD-CWE-noinfo"}],"source":"nvd@nist.gov","type":"Primary"}]},"severity":"MEDIUM","source":"nvd","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Clear stale exiting pointer in futex_lock..."}