CVE-2025-39977 (GCVE-0-2025-39977)

Vulnerability from cvelistv5 – Published: 2025-10-15 07:55 – Updated: 2026-05-12 12:07
VLAI
Title
futex: Prevent use-after-free during requeue-PI
Summary
In 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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 07d91ef510fb16a2e0ca7453222105835b7ba3b8 , < cb5d19a61274b51b49601214a87af573b43d60fa (git)
Affected: 07d91ef510fb16a2e0ca7453222105835b7ba3b8 , < 348736955ed6ca6e99ca24b93b1d3fbfe352c181 (git)
Affected: 07d91ef510fb16a2e0ca7453222105835b7ba3b8 , < a170b9c0dde83312b8b58ccc91509c7c15711641 (git)
Affected: 07d91ef510fb16a2e0ca7453222105835b7ba3b8 , < d824b2dbdcfe3c390278dd9652ea526168ef6850 (git)
Affected: 07d91ef510fb16a2e0ca7453222105835b7ba3b8 , < b549113738e8c751b613118032a724b772aa83f2 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.1.155 , ≤ 6.1.* (semver)
Unaffected: 6.6.109 , ≤ 6.6.* (semver)
Unaffected: 6.12.50 , ≤ 6.12.* (semver)
Unaffected: 6.16.10 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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Detection rules are retrieved from Rulezet.