Linux KernelOperating system · Linux
CVE-2026-52977
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: futex: Prevent lockup in requeue-PI during signal/ timeout wakeup During wait-requeue-pi (task A) and requeue-PI (task B) the following race can happen: Task A Task B futex_wait_requeue_pi() futex_setup_timer() futex_do_wait() futex_requeue() CLASS(hb, hb1)(&key1); CLASS(hb, hb2)(&key2); *timeout* futex_requeue_pi_wakeup_sync() requeue_state = Q_REQUEUE_PI_IGNORE *blocks on hb->lock* futex_proxy_trylock_atomic() futex_requeue_pi_prepare() Q_REQUEUE_PI_IGNORE => -EAGAIN double_unlock_hb(hb1, hb2) *retry* Task B acquires both hb locks and attempts to acquire the PI-lock of the top most waiter (task B). Task A is leaving early due to a signal/ timeout and started removing itself from the queue. It updates its requeue_state but can not remove it from the list because this requires the hb lock which is owned by task B. Usually task A is able to swoop the lock after task B unlocked it. However if task B is of higher priority then task A may not be able to wake up in time and acquire the lock before task B gets it again. Especially on a UP system where A is never scheduled. As a result task A blocks on the lock and task B busy loops, trying to make progress but live locks the system instead. Tragic. This can be fixed by removing the top most waiter from the list in this case. This allows task B to grab the next top waiter (if any) in the next iteration and make progress. Remove the top most waiter if futex_requeue_pi_prepare() fails. Let the waiter conditionally remove itself from the list in handle_early_requeue_pi_wakeup().
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA race condition in the Linux kernel's futex requeue-PI implementation can cause a live-lock scenario where Task A (waiting with timeout/signal) and Task B (requeue-PI) both block indefinitely. Task A cannot remove itself from the queue due to lock contention while Task B holds both hash bucket locks, preventing Task A from waking and acquiring the PI lock, especially on UP systems.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 5.15, < 6.1.175>= 6.2, < 6.6.141>= 6.7, < 6.12.91>= 6.13, < 6.18.33>= 6.19, < 7.0.10= 7.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed kernel versionRun `uname -r` or `cat /proc/version` to get the running kernel versionAffected if The version falls within any of these ranges: >= 5.15 and < 6.1.175, >= 6.2 and < 6.6.141, >= 6.7 and < 6.12.91, >= 6.13 and < 6.18.33, >= 6.19 and < 7.0.10, or equals exactly 7.1
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Identify system processor countRun `nproc` or check `/proc/cpuinfo` to determine the number of processorsAffected if System is a uniprocessor (UP) configuration, as the advisory specifically notes this condition is more easily triggered on UP systems
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Verify if futex requeue-PI is in useAudit running processes and applications that use futex operations with PI (priority inheritance) requeue semantics; this is typically found in threading libraries, synchronization primitives, or real-time applications. Check application code for calls involving FUTEX_CMP_REQUEUE_PI or FUTEX_WAKE_OP with PI flags.Affected if Applications or libraries using futex requeue-PI operations are running on the affected kernel, as the race condition requires both Task A (waiting with timeout/signal) and Task B (requeue-PI) to be active on the same hash bucket
A system is affected if it runs a kernel version in the affected ranges AND executes workloads that trigger the futex requeue-PI code path with concurrent waiters, particularly on UP systems.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped6.1.1756.6.1416.12.91
Apply the kernel patch that modifies futex_requeue_pi_prepare() to remove the topmost waiter on failure and updates handle_early_requeue_pi_wakeup() to conditionally remove waiters from the list, enabling progress.
Upgrade to kernel version 6.1.175 (or later 6.1.x), 6.6.141 (or later 6.6.x), 6.12.91 (or later 6.12.x), or 6.18.33 (or later 6.18.x) depending on your distribution's supported branch
- Identify the current running kernel version using `uname -r`
- Check which stable kernel branch is appropriate for your system (e.g., 6.1.x, 6.6.x, 6.12.x, or 6.18.x)
- Obtain the fixed kernel version for your branch: 6.1.175 or later, 6.6.141 or later, 6.12.91 or later, or 6.18.33 or later
- Upgrade the Linux kernel package via your distribution's package manager (e.g., `apt-get dist-upgrade`, `yum update`, or `dnf upgrade`)
- Reboot the system to load the patched kernel
- Verify the new kernel version is running with `uname -r`
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA6.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-52977 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-52977 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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