futex: Prevent use-after-free during requeue-PI

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-39977
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-10-15 08:15:35 UTC
Updated2026-07-14 13:17:51 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: futex: Prevent use-after-free during requeue-PI syzbot managed to trigger the following race: T1 T2 futex_wait_requeue_pi() futex_do_wait() schedule() futex_requeue() futex_proxy_trylock_atomic() futex_requeue_pi_prepare() requeue_pi_wake_futex() futex_requeue_pi_complete() /* preempt */ * timeout/ signal wakes T1 * futex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED futex_hash_put() // back to userland, on stack futex_q is garbage /* back */ wake_up_state(q->task, TASK_NORMAL); In this scenario futex_wait_requeue_pi() is able to leave without using futex_q::lock_ptr for synchronization. This can be prevented by reading futex_q::task before updating the futex_q::requeue_state. A reference on the task_struct is not needed because requeue_pi_wake_futex() is invoked with a spinlock_t held which implies a RCU read section. Even if T1 terminates immediately after, the task_struct will remain valid during T2's wake_up_state(). A READ_ONCE on futex_q::task before futex_requeue_pi_complete() is enough because it ensures that the variable is read before the state is updated. Read futex_q::task before updating the requeue state, use it for the following wakeup.

Risk And Classification

EPSS: 0.001930000 probability, percentile 0.090890000 (date 2026-07-14)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 cb5d19a61274b51b49601214a87af573b43d60fa git Not specified
CNA Linux Linux affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 348736955ed6ca6e99ca24b93b1d3fbfe352c181 git Not specified
CNA Linux Linux affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 a170b9c0dde83312b8b58ccc91509c7c15711641 git Not specified
CNA Linux Linux affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 d824b2dbdcfe3c390278dd9652ea526168ef6850 git Not specified
CNA Linux Linux affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 b549113738e8c751b613118032a724b772aa83f2 git Not specified
CNA Linux Linux affected 5.15 Not specified
CNA Linux Linux unaffected 5.15 semver Not specified
CNA Linux Linux unaffected 6.1.155 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.109 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.50 6.12.* semver Not specified
CNA Linux Linux unaffected 6.16.10 6.16.* semver Not specified
CNA Linux Linux unaffected 6.17 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.5 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified

References

ReferenceSourceLinkTags
cert-portal.siemens.com/productcert/html/ssa-082556.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
cert-portal.siemens.com/productcert/html/ssa-019113.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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