CVE-2026-90003
CVE-2026-90003 is a security vulnerability. O3 Security confirms whether CVE-2026-90003 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
In the Linux kernel, the following vulnerability has been resolved: futex: Prevent rcuwait use-after-free during requeue PI On PREEMPT_RT, FUTEX_CMP_REQUEUE_PI can trigger a KASAN…
Description
In the Linux kernel, the following vulnerability has been resolved:
futex: Prevent rcuwait use-after-free during requeue PI
On PREEMPT_RT, FUTEX_CMP_REQUEUE_PI can trigger a KASAN report (slab-out-of-bounds) in futex_requeue_pi_complete() invocation of rcuwait_wake_up().
The futex_q used by futex_wait_requeue_pi() is allocated on the waiter's stack. An early wakeup can race with a PI requeue as follows:
waiter requeue task
------ ------------
futex_wait_requeue_pi() futex_do_wait() schedule() futex_requeue futex_proxy_trylock_atomic() futex_requeue_pi_prepare() Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_IN_PROGRESS
- timeout/ signal wakes waiter * futex_requeue_pi_wakeup_sync() Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_WAIT requeue_pi_wake_futex futex_requeue_pi_complete() cmpxchg Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_LOCKED rcuwait_wait_event() if (atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT) break /* no schedule() */
/* q.pi_state->owner == current / futex_private_hash_put() / return from syscall / rcuwait_wake_up(&q->requeue_wait) / q is gone */
futex_requeue_pi_complete() publishes Q_REQUEUE_PI_LOCKED before calling rcuwait_wake_up(). The waiter observes this state in rcuwait_wait_event() before invoking schedule() in rcuwait_wait_event(). Here, the waiter is free leave the syscall before requeue task can complete the wake.
To address this race skip rcuwait_wake_up() in the Q_REQUEUE_PI_LOCKED case. This state is only published by requeue_pi_wake_futex(), which saves q->task before futex_requeue_pi_complete() and wakes the waiter via wake_up_state().
This wake is intended to wake the waiter from its futex_do_wait() sleep. If the waiter is still sleeping there, it can not get into the Q_REQUEUE_PI_WAIT state (and require this removed wake). Should the waiter be woken up from futex_do_wait() by other means (as in this example) and sleep in futex_requeue_pi_wakeup_sync() then the wake_up_state() from requeue_pi_wake_futex() will wake it, too. Should the waiter task terminate before wake_up_state() had a chance to wake the task then the task pointer does not become invalid because the futex_hash_bucket::lock is held and the task pointer is RCU protected.
[bigeasy: Updated comment and commit message]
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-90003 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-90003 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-90003. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-90003 in your dependencies?
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