{"id":"AZL-68525","summary":"CVE-2025-39977 affecting package kernel for versions less than 6.6.112.1-1","details":"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-\u003etask, 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.","modified":"2026-04-01T05:21:26.609652Z","published":"2025-10-15T08:15:35Z","upstream":["CVE-2025-39977"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39977"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.112.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-68525.json"}}],"schema_version":"1.7.5"}