CVE-2025-39977

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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."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - The race is driven entirely through the futex(2) syscall (FUTEX_WAIT_REQUEUE_PI on one thread, FUTEX_CMP_REQUEUE_PI on another), which requires local execution on the target system. There is no remote or adjacent-network path into kernel/futex/requeue.c.\nAC:L - The attacker controls both sides of the race: it creates the waiter thread with an attacker-chosen short timeout (or delivers a signal) and simultaneously issues the requeue from a second thread, and can retry the loop millions of times with CPU pinning and interrupt pressure to hit the window between futex_requeue_pi_complete() and wake_up_state(). syzbot hit it with random fuzzing, and on PREEMPT_RT the hb spinlock_t is preemptible, making the window wide.\nPR:L - Any unprivileged local user can call futex() with FUTEX_WAIT_REQUEUE_PI/FUTEX_CMP_REQUEUE_PI; do_futex() and futex_requeue() contain no capability or credential checks, and CONFIG_FUTEX_PI is default-y. The path is reachable from inside containers and sandboxes with no elevated privileges.\nUI:N - The attacker's own two threads perform every step of the exploit; no victim action, mount, or file open is involved.\nS:U - The corruption occurs in kernel memory (a stale kernel stack frame and a type-confused task_struct) and stays within the kernel's own security authority. No VM, IOMMU, or hypervisor boundary is crossed.\nC:H - This is a use-after-free read of the waiter's dead kernel stack frame, and the resulting attacker-influenced task_struct pointer is dereferenced in try_to_wake_up() (p->__state, p->saved_state, p->on_rq, p->sched_class), giving an arbitrary kernel-memory read/oracle primitive. Per UAF guidance this is High.\nI:H - The stale futex_q lives on the attacker's own kernel stack, which can be refilled with controlled bytes by an immediately following syscall, so q->task becomes an attacker-chosen pointer; try_to_wake_up() then writes to it (raw_spin_lock on p->pi_lock, WRITE_ONCE(p->__state, TASK_RUNNING), runqueue list manipulation) and makes an indirect call through p->sched_class->enqueue_task(), a plausible local privilege-escalation path.\nA:H - In the unexploited case wake_up_state() dereferences a wild pointer from reused stack memory, causing an immediate oops/panic, and corrupting scheduler runqueue state can hang the machine. Any use-after-free of this kind is a High availability impact."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/futex/requeue.c"], "versions": [{"version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "cb5d19a61274b51b49601214a87af573b43d60fa", "status": "affected", "versionType": "git"}, {"version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "348736955ed6ca6e99ca24b93b1d3fbfe352c181", "status": "affected", "versionType": "git"}, {"version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "a170b9c0dde83312b8b58ccc91509c7c15711641", "status": "affected", "versionType": "git"}, {"version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "d824b2dbdcfe3c390278dd9652ea526168ef6850", "status": "affected", "versionType": "git"}, {"version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "b549113738e8c751b613118032a724b772aa83f2", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/futex/requeue.c"], "versions": [{"version": "5.15", "status": "affected"}, {"version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.155", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.109", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.50", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.10", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.1.155"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.109"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.50"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.16.10"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.17"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa"}, {"url": "https://git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181"}, {"url": "https://git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641"}, {"url": "https://git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850"}, {"url": "https://git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2"}], "title": "futex: Prevent use-after-free during requeue-PI", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"x_adpType": "supplier", "providerMetadata": {"orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "shortName": "siemens-SADP", "dateUpdated": "2026-11-10T12:37:24.327Z"}, "affected": [{"vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "versions": [{"status": "affected", "version": "V3.1.5", "lessThan": "*", "versionType": "custom"}], "defaultStatus": "unknown"}, {"vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "versions": [{"status": "affected", "version": "V3.1.6", "lessThan": "*", "versionType": "custom"}], "defaultStatus": "unknown"}, {"vendor": 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"https://cert-portal.siemens.com/productcert/html/ssa-082556.html"}, {"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"}, {"url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}]}, {"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2025-39977", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-15T21:55:38.918885Z"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-15T22:02:35.093Z"}}]}}

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There is no remote or adjacent-network path into kernel/futex/requeue.c.\nAC:L - The attacker controls both sides of the race: it creates the waiter thread with an attacker-chosen short timeout (or delivers a signal) and simultaneously issues the requeue from a second thread, and can retry the loop millions of times with CPU pinning and interrupt pressure to hit the window between futex_requeue_pi_complete() and wake_up_state(). syzbot hit it with random fuzzing, and on PREEMPT_RT the hb spinlock_t is preemptible, making the window wide.\nPR:L - Any unprivileged local user can call futex() with FUTEX_WAIT_REQUEUE_PI/FUTEX_CMP_REQUEUE_PI; do_futex() and futex_requeue() contain no capability or credential checks, and CONFIG_FUTEX_PI is default-y. The path is reachable from inside containers and sandboxes with no elevated privileges.\nUI:N - The attacker's own two threads perform every step of the exploit; no victim action, mount, or file open is involved.\nS:U - The corruption occurs in kernel memory (a stale kernel stack frame and a type-confused task_struct) and stays within the kernel's own security authority. No VM, IOMMU, or hypervisor boundary is crossed.\nC:H - This is a use-after-free read of the waiter's dead kernel stack frame, and the resulting attacker-influenced task_struct pointer is dereferenced in try_to_wake_up() (p->__state, p->saved_state, p->on_rq, p->sched_class), giving an arbitrary kernel-memory read/oracle primitive. Per UAF guidance this is High.\nI:H - The stale futex_q lives on the attacker's own kernel stack, which can be refilled with controlled bytes by an immediately following syscall, so q->task becomes an attacker-chosen pointer; try_to_wake_up() then writes to it (raw_spin_lock on p->pi_lock, WRITE_ONCE(p->__state, TASK_RUNNING), runqueue list manipulation) and makes an indirect call through p->sched_class->enqueue_task(), a plausible local privilege-escalation path.\nA:H - In the unexploited case wake_up_state() dereferences a wild pointer from reused stack memory, causing an immediate oops/panic, and corrupting scheduler runqueue state can hang the machine. Any use-after-free of this kind is a High availability impact."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "cb5d19a61274b51b49601214a87af573b43d60fa", "versionType": "git"}, {"status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "348736955ed6ca6e99ca24b93b1d3fbfe352c181", "versionType": "git"}, {"status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "a170b9c0dde83312b8b58ccc91509c7c15711641", "versionType": "git"}, {"status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "d824b2dbdcfe3c390278dd9652ea526168ef6850", "versionType": "git"}, {"status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "lessThan": "b549113738e8c751b613118032a724b772aa83f2", "versionType": "git"}], "programFiles": ["kernel/futex/requeue.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "5.15"}, {"status": "unaffected", "version": "0", "lessThan": "5.15", "versionType": "semver"}, {"status": "unaffected", "version": "6.1.155", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.109", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.12.50", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.16.10", "versionType": "semver", "lessThanOrEqual": "6.16.*"}, {"status": "unaffected", "version": "6.17", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["kernel/futex/requeue.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa"}, {"url": "https://git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181"}, {"url": "https://git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641"}, {"url": "https://git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850"}, {"url": "https://git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "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."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.155", "versionStartIncluding": "5.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.109", "versionStartIncluding": "5.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.50", "versionStartIncluding": "5.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.16.10", "versionStartIncluding": "5.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.17", "versionStartIncluding": "5.15"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:06:46.111Z"}}}, "cveMetadata": {"cveId": "CVE-2025-39977", "state": "PUBLISHED", "dateUpdated": "2026-11-10T12:37:24.327Z", "dateReserved": "2025-04-16T07:20:57.150Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2025-10-15T07:55:58.283Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["kernel/futex/requeue.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "cb5d19a61274b51b49601214a87af573b43d60fa", "status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "versionType": "git"}, {"lessThan": "348736955ed6ca6e99ca24b93b1d3fbfe352c181", "status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "versionType": "git"}, {"lessThan": "a170b9c0dde83312b8b58ccc91509c7c15711641", "status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "versionType": "git"}, {"lessThan": "d824b2dbdcfe3c390278dd9652ea526168ef6850", "status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "versionType": "git"}, {"lessThan": "b549113738e8c751b613118032a724b772aa83f2", "status": "affected", "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["kernel/futex/requeue.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.15"}, {"lessThan": "5.15", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.155", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.109", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.50", "versionType": "semver"}, {"lessThanOrEqual": "6.16.*", "status": "unaffected", "version": "6.16.10", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "6.17", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"affectedData": [{"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}], "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfutex: Prevenir uso despu\u00e9s de liberaci\u00f3n durante requeue-PI\n\nsyzbot logr\u00f3 activar la siguiente condici\u00f3n de carrera:\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 * el tiempo de espera/la se\u00f1al despierta a T1 *\n\n futex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED\n futex_hash_put()\n // de vuelta al espacio de usuario, en la pila futex_q es basura\n\n /* de vuelta */\n wake_up_state(q->task, TASK_NORMAL);\n\nEn este escenario, futex_wait_requeue_pi() puede salir sin usar futex_q::lock_ptr para la sincronizaci\u00f3n.\n\nEsto puede prevenirse leyendo futex_q::task antes de actualizar el futex_q::requeue_state. No se necesita una referencia en el task_struct porque se invoca a requeue_pi_wake_futex() con un spinlock_t mantenido, lo que implica una secci\u00f3n de lectura RCU.\n\nIncluso si T1 termina inmediatamente despu\u00e9s, el task_struct permanecer\u00e1 v\u00e1lido durante el wake_up_state() de T2. Un READ_ONCE en futex_q::task antes de futex_requeue_pi_complete() es suficiente porque asegura que la variable se lee antes de que se actualice el estado.\n\nLeer futex_q::task antes de actualizar el estado de requeue, usarlo para la siguiente activaci\u00f3n."}], "id": "CVE-2025-39977", "lastModified": "2026-11-10T13:17:53.363", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2025-39977", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-15T21:55:38.918885Z", "version": "2.0.3"}}]}, "published": "2025-10-15T08:15:35.517", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850"}, {"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"}, {"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"}, {"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Deferred"}

{"bugzilla": {"description": "kernel: futex: Prevent use-after-free during requeue-PI", "id": "2404113", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2404113"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nfutex: Prevent use-after-free during requeue-PI\nsyzbot managed to trigger the following race:\nT1 T2\nfutex_wait_requeue_pi()\nfutex_do_wait()\nschedule()\nfutex_requeue()\nfutex_proxy_trylock_atomic()\nfutex_requeue_pi_prepare()\nrequeue_pi_wake_futex()\nfutex_requeue_pi_complete()\n/* preempt */\n* timeout/ signal wakes T1 *\nfutex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED\nfutex_hash_put()\n// back to userland, on stack futex_q is garbage\n/* back */\nwake_up_state(q->task, TASK_NORMAL);\nIn this scenario futex_wait_requeue_pi() is able to leave without using\nfutex_q::lock_ptr for synchronization.\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.\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.\nRead futex_q::task before updating the requeue state, use it for the\nfollowing wakeup."], "name": "CVE-2025-39977", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-10-15T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-39977\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-39977\nhttps://lore.kernel.org/linux-cve-announce/2025101558-CVE-2025-39977-b3a2@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-10-20T13:26:49.677872+00:00", "updated": "2025-10-20T13:26:49.677897+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}