5.5

CVE-2026-52977: futex: Prevent lockup in requeue-PI during signal/ timeout wakeup

Modified
AliasesUBUNTU-CVE-2026-52977DEBIAN-CVE-2026-52977
Published 24-06-2026Last modified 19-08-2026

Vulnerability summary

CVE-2026-52977 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.12% chance of exploitation in the next 30 days, higher than 2% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.12%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 48 · Related 47
OPENSUSE-SU-2026:21910-1RHSA-2026:51035SUSE-SU-2026:23477-1SUSE-SU-2026:23481-1SUSE-SU-2026:23528-1SUSE-SU-2026:23529-1

Timeline

  1. 24-06-2026
    PublishedVulnerability first disclosed.
  2. 19-08-2026
    Last modifiedVulnerability information updated.

Description

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().

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.12%

Chance of exploitation in the next 30 days

Percentile

2%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.12% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu154 products
  • linux< 5.15.0-198.208 | < 6.8.0-136.136 | All versions (No fix recorded) | < 7.0.0-28.28
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 5.15.0-1117.124 | < 6.8.0-1061.64 | All versions (No fix recorded) | < 7.0.0-1009.9
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c | ≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < 4e0ed44e51727d56244a822ab941efe507c47966 | ≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < e3f95b1ba242e37093305812df7fdbe7288a43ac | ≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < 0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf | ≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < 69a7cfc66405aeaa2483147653d031b3592ffc9c | ≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < 0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0 | ≥ 07d91ef510fb16a2e0ca7453222105835b7ba3b8, < bc7304f3ae20972d11db6e0b1b541c63feda5f05 | 5.15
  • linux_kernel≥ 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 | 7.1:rc1
Debian1 product
  • linux< 6.1.176-1 | < 6.12.94-1 | < 7.0.10-1

3 vendors · 157 products

References

43 links
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