---
id: CVE-2026-52977
title: |-
  In 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  …
summary: |-
  In 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  …
severity: medium
published: '2026-06-24'
updated: '2026-07-10'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52977'
references:
  - url: 'https://git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52977.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-52977'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2492351'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-52977'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52977'
  - url: >-
      https://lore.kernel.org/linux-cve-announce/2026062440-CVE-2026-52977-deda@gregkh/T
  - url: 'https://access.redhat.com/errata/RHSA-2026:51035'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
epss: 0.00162
epssPercentile: 0.04802
ingestedAt: '2026-07-11T13:13:25.199Z'
vendor: Red Hat
product: Red Hat Enterprise Linux BaseOS (v. 9)
affected:
  - enterprise_linux 10
  - enterprise_linux 9
  - enterprise_linux_appstream_v_9
  - enterprise_linux_baseos_v_9
  - enterprise_linux_codeready_linux_builder_v_9
  - enterprise_linux_real_time_for_nfv_v_9
  - enterprise_linux_real_time_v_9
patched:
  - enterprise_linux_appstream_v_9
  - enterprise_linux_baseos_v_9
  - enterprise_linux_codeready_linux_builder_v_9
  - enterprise_linux_real_time_for_nfv_v_9
  - enterprise_linux_real_time_v_9
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: vendor
cwe:
  - CWE-364
---

## Overview

In 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().

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2026:51035** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-08-06 · [advisory](https://access.redhat.com/errata/RHSA-2026:51035)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52977.json)