{"id":"CVE-2026-52977","title":"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  …","summary":"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  …","severity":"medium","published":"2026-06-24","updated":"2026-07-10","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-52977","references":[{"url":"https://git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52977.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-52977"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2492351"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-52977"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52977"},{"url":"https://lore.kernel.org/linux-cve-announce/2026062440-CVE-2026-52977-deda@gregkh/T"},{"url":"https://access.redhat.com/errata/RHSA-2026:51035"}],"tags":["nvd","csaf","vex","red-hat"],"epss":0.00162,"epssPercentile":0.04786,"ingestedAt":"2026-07-11T13:13:25.199Z","vendor":"Red Hat","product":"Red Hat Enterprise Linux BaseOS (v. 9)","affected":["enterprise_linux 10","enterprise_linux 9","enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_9"],"patched":["enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_9"],"cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":["CWE-364"],"slug":"CVE-2026-52977","body":"## Overview\n\nIn 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().\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:51035** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-08-06 · [advisory](https://access.redhat.com/errata/RHSA-2026:51035)\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52977.json)","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":205506,"id":"CVE-2026-52977","ts":1789576722561,"field":"cvss","old":null,"new":"5.5"},{"seq":205505,"id":"CVE-2026-52977","ts":1789576722561,"field":"severity","old":"none","new":"medium"}]}