{"id":"CVE-2026-52977","state":"PUBLISHED","title":"futex: Prevent lockup in requeue-PI during signal/ timeout wakeup","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent lockup in requeue-PI during signal/ timeout wakeup\n\nDuring wait-requeue-pi (task A) and requeue-PI (task B) the following\nrace can happen:\n\n     Task A                             Task B\n  futex_wait_requeue_pi()\n    futex_setup_timer()\n    futex_do_wait()\n                                   futex_requeue()\n                                        CLASS(hb, hb1)(&key1);\n                                        CLASS(hb, hb2)(&key2);\n        *timeout*\n    futex_requeue_pi_wakeup_sync()\n        requeue_state = Q_REQUEUE_PI_IGNORE\n\n    *blocks on hb->lock*\n\n                                        futex_proxy_trylock_atomic()\n                                          futex_requeue_pi_prepare()\n                                            Q_REQUEUE_PI_IGNORE => -EAGAIN\n                                        double_unlock_hb(hb1, hb2)\n                                         *retry*\n\nTask B acquires both hb locks and attempts to acquire the PI-lock of the\ntop most waiter (task B). Task A is leaving early due to a signal/\ntimeout and started removing itself from the queue. It updates its\nrequeue_state but can not remove it from the list because this requires\nthe hb lock which is owned by task B.\n\nUsually task A is able to swoop the lock after task B unlocked it.\nHowever if task B is of higher priority then task A may not be able to\nwake up in time and acquire the lock before task B gets it again.\nEspecially on a UP system where A is never scheduled.\n\nAs a result task A blocks on the lock and task B busy loops, trying to\nmake progress but live locks the system instead. Tragic.\n\nThis can be fixed by removing the top most waiter from the list in this\ncase. This allows task B to grab the next top waiter (if any) in the\nnext iteration and make progress.\n\nRemove the top most waiter if futex_requeue_pi_prepare() fails.\nLet the waiter conditionally remove itself from the list in\nhandle_early_requeue_pi_wakeup().","publishedAt":"2026-06-24T16:28:53.937Z","updatedAt":"2026-08-19T16:28:04.076Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"4e0ed44e51727d56244a822ab941efe507c47966","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"e3f95b1ba242e37093305812df7fdbe7288a43ac","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"69a7cfc66405aeaa2483147653d031b3592ffc9c","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"bc7304f3ae20972d11db6e0b1b541c63feda5f05","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/requeue.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.175","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.141","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.91","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.33","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.10","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/requeue.c"]}],"references":["https://git.kernel.org/stable/c/e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c","https://git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966","https://git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac","https://git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf","https://git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c","https://git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0","https://git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/52xxx/CVE-2026-52977.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-52977","state":"PUBLISHED","datePublished":"2026-06-24T16:28:53.937Z","dateUpdated":"2026-08-19T16:28:04.076Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-06-09T07:44:35.376Z"},"containers":{"cna":{"title":"futex: Prevent lockup in requeue-PI during signal/ timeout wakeup","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent lockup in requeue-PI during signal/ timeout wakeup\n\nDuring wait-requeue-pi (task A) and requeue-PI (task B) the following\nrace can happen:\n\n     Task A                             Task B\n  futex_wait_requeue_pi()\n    futex_setup_timer()\n    futex_do_wait()\n                                   futex_requeue()\n                                        CLASS(hb, hb1)(&key1);\n                                        CLASS(hb, hb2)(&key2);\n        *timeout*\n    futex_requeue_pi_wakeup_sync()\n        requeue_state = Q_REQUEUE_PI_IGNORE\n\n    *blocks on hb->lock*\n\n                                        futex_proxy_trylock_atomic()\n                                          futex_requeue_pi_prepare()\n                                            Q_REQUEUE_PI_IGNORE => -EAGAIN\n                                        double_unlock_hb(hb1, hb2)\n                                         *retry*\n\nTask B acquires both hb locks and attempts to acquire the PI-lock of the\ntop most waiter (task B). Task A is leaving early due to a signal/\ntimeout and started removing itself from the queue. It updates its\nrequeue_state but can not remove it from the list because this requires\nthe hb lock which is owned by task B.\n\nUsually task A is able to swoop the lock after task B unlocked it.\nHowever if task B is of higher priority then task A may not be able to\nwake up in time and acquire the lock before task B gets it again.\nEspecially on a UP system where A is never scheduled.\n\nAs a result task A blocks on the lock and task B busy loops, trying to\nmake progress but live locks the system instead. Tragic.\n\nThis can be fixed by removing the top most waiter from the list in this\ncase. This allows task B to grab the next top waiter (if any) in the\nnext iteration and make progress.\n\nRemove the top most waiter if futex_requeue_pi_prepare() fails.\nLet the waiter conditionally remove itself from the list in\nhandle_early_requeue_pi_wakeup()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"4e0ed44e51727d56244a822ab941efe507c47966","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"e3f95b1ba242e37093305812df7fdbe7288a43ac","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"69a7cfc66405aeaa2483147653d031b3592ffc9c","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0","versionType":"git"},{"version":"07d91ef510fb16a2e0ca7453222105835b7ba3b8","status":"affected","lessThan":"bc7304f3ae20972d11db6e0b1b541c63feda5f05","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/requeue.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.175","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.141","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.91","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.33","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.10","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/requeue.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c"},{"url":"https://git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966"},{"url":"https://git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac"},{"url":"https://git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf"},{"url":"https://git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c"},{"url":"https://git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0"},{"url":"https://git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-19T16:28:04.076Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.175"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.141"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.91"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.33"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.0.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}