{"id":"CVE-2025-39977","revision":"8148fb2a79104bd5ac4ca09bbf0fea4d","records":[{"revision":"8148fb2a79104bd5ac4ca09bbf0fea4d","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2025-39977","aliases":[],"title":"futex: Prevent use-after-free during requeue-PI","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent use-after-free during requeue-PI\n\nsyzbot managed to trigger the following race:\n\n   T1                               T2\n\n futex_wait_requeue_pi()\n   futex_do_wait()\n     schedule()\n                               futex_requeue()\n                                 futex_proxy_trylock_atomic()\n                                   futex_requeue_pi_prepare()\n                                   requeue_pi_wake_futex()\n                                     futex_requeue_pi_complete()\n                                      /* preempt */\n\n         * timeout/ signal wakes T1 *\n\n   futex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED\n   futex_hash_put()\n  // back to userland, on stack futex_q is garbage\n\n                                      /* back */\n                                     wake_up_state(q->task, TASK_NORMAL);\n\nIn this scenario futex_wait_requeue_pi() is able to leave without using\nfutex_q::lock_ptr for synchronization.\n\nThis can be prevented by reading futex_q::task before updating the\nfutex_q::requeue_state. A reference on the task_struct is not needed\nbecause requeue_pi_wake_futex() is invoked with a spinlock_t held which\nimplies a RCU read section.\n\nEven if T1 terminates immediately after, the task_struct will remain valid\nduring T2's wake_up_state().  A READ_ONCE on futex_q::task before\nfutex_requeue_pi_complete() is enough because it ensures that the variable\nis read before the state is updated.\n\nRead futex_q::task before updating the requeue state, use it for the\nfollowing wakeup.","state":0,"publishedAt":"2025-10-15T07:55:58.283+00:00","modifiedAt":"2026-10-15T22:02:35.093+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"kernel/futex/requeue.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"07d91ef510fb16a2e0ca7453222105835b7ba3b8\",\n                            \"lessThan\": \"cb5d19a61274b51b49601214a87af573b43d60fa\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"07d91ef510fb16a2e0ca7453222105835b7ba3b8\",\n                            \"lessThan\": \"348736955ed6ca6e99ca24b93b1d3fbfe352c181\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"07d91ef510fb16a2e0ca7453222105835b7ba3b8\",\n                            \"lessThan\": \"a170b9c0dde83312b8b58ccc91509c7c15711641\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"07d91ef510fb16a2e0ca7453222105835b7ba3b8\",\n                            \"lessThan\": \"d824b2dbdcfe3c390278dd9652ea526168ef6850\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"07d91ef510fb16a2e0ca7453222105835b7ba3b8\",\n                            \"lessThan\": \"b549113738e8c751b613118032a724b772aa83f2\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"kernel/futex/requeue.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.15\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.15\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.155\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.109\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.50\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.16.10\",\n                            \"lessThanOrEqual\": \"6.16.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.17\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa","https://git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181","https://git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641","https://git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850","https://git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39977","license":"CVE Program Terms of Use","key":"cve-program:CVE-2025-39977","identifiers":["CVE-2025-39977"]},"retained":false,"historicalAffected":[]}],"coverage":[]}