{"api_version":"1","generated_at":"2026-07-24T19:51:32+00:00","cve":"CVE-2026-31555","urls":{"html":"https://cve.report/CVE-2026-31555","api":"https://cve.report/api/cve/CVE-2026-31555.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31555","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31555"},"summary":{"title":"futex: Clear stale exiting pointer in futex_lock_pi() retry path","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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-04-24 15:16:29","updated_at":"2026-07-14 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:*:*:*:*:*:*:*:*","versionStartIncluding":"4.4.255","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9.255","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14.158","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.172","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.1","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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."}],"providerMetadata":{"dateUpdated":"2026-05-23T16:05:19.706Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa"},{"url":"https://git.kernel.org/stable/c/e7824ec168d2ac883a213cd1f4d6cc0816002a85"},{"url":"https://git.kernel.org/stable/c/5e8e06bf8909e79b4acd950cf578cfc2f10bbefa"},{"url":"https://git.kernel.org/stable/c/de7c0c04ad868f2cee6671b11c0a6d20421af1da"},{"url":"https://git.kernel.org/stable/c/7475dfad10a05a5bfadebf5f2499bd61b19ed293"},{"url":"https://git.kernel.org/stable/c/92e47ad03e03dbb5515bdf06444bf6b1e147310d"},{"url":"https://git.kernel.org/stable/c/71112e62807d1925dc3ae6188b11f8cfc85aec23"},{"url":"https://git.kernel.org/stable/c/210d36d892de5195e6766c45519dfb1e65f3eb83"}],"title":"futex: Clear stale exiting pointer in futex_lock_pi() retry path","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-31555","datePublished":"2026-04-24T14:35:39.211Z","dateReserved":"2026-03-09T15:48:24.115Z","dateUpdated":"2026-07-14T12:48:20.561Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-24 15:16:29","lastModifiedDate":"2026-07-14 13:18:45","problem_types":["NVD-CWE-noinfo"],"metrics":{"cvssMetricV31":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","baseScore":5.5,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":3.6}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.4.255","versionEndExcluding":"4.5","matchCriteriaId":"39A57944-7654-4465-9F2B-4DC1CB18ADFB"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.9.255","versionEndExcluding":"4.10","matchCriteriaId":"F932A542-7872-4F86-AD1E-00CCC240C25D"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14.158","versionEndExcluding":"4.15","matchCriteriaId":"C62F59A2-9EFC-4E7F-B9E7-3DFF4E885406"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.172","versionEndExcluding":"4.20","matchCriteriaId":"235BE773-4E0B-4AD6-9314-D176A65C4B73"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.1","versionEndExcluding":"5.5","matchCriteriaId":"025DC0BA-08A8-4703-AE9F-7C3D8E346A45"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.5.1","versionEndExcluding":"5.10.253","matchCriteriaId":"45E871E1-B00E-4E88-83A3-60B38EAF2B8A"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"5.15.203","matchCriteriaId":"20DDB3E9-AABF-4107-ADB0-5362AA067045"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.1.168","matchCriteriaId":"E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.6.131","matchCriteriaId":"CE6ED4D4-0046-4573-BFA9-D64143B6A89F"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.80","matchCriteriaId":"97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.18.21","matchCriteriaId":"ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"6.19.11","matchCriteriaId":"4CA2E747-A9EC-4518-9AA2-B4247FC748B7"},{"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"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31555","Ordinal":"1","Title":"futex: Clear stale exiting pointer in futex_lock_pi() retry path","CVE":"CVE-2026-31555","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31555","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"futex: Clear stale exiting pointer in futex_lock_pi() retry path"}]}}}