CVE-2025-21631

Privilege escalation via stale BFQ waker queue

Published Jan 19, 2025 · Updated Aug 5, 2026

Use-after-free in affected Linux kernel releases' BFQ I/O scheduler allows local users to escalate privileges through normal file I/O. bfq_split_bfqq() releases a process reference without clearing a stale waker_bfqq pointer, and bfq_init_rq() later inserts the freed queue into a list. Any unprivileged local user can reach the path when BFQ is active, enabling kernel-memory disclosure, arbitrary writes, privilege escalation, or a kernel panic.

CVSS severity7.8
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in affected Linux kernel releases' BFQ I/O scheduler allows local users to escalate privileges through normal file I/O. bfq_split_bfqq() releases a process reference without clearing a stale waker_bfqq pointer, and bfq_init_rq() later inserts the freed queue into a list. Any unprivileged local user can reach the path when BFQ is active, enabling kernel-memory disclosure, arbitrary writes, privilege escalation, or a kernel panic.

The record

CVE
CVE-2025-21631
Published
Jan 19, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0780451f03bf518bc032a7c584de8f92e2d39d7f <be3eed59ac01f429ac10aaa46e26f653bcf581ab
  2. Affected versionversion=0b8bda0ff17156cd3f60944527c9d8c9f99f1583
  3. Affected versionversion=1ba0403ac6447f2d63914fb760c44a3b19c44eaf <bc2aeb35ff167e0c6b0cedf0c96a5c41e6cba1ed
  4. Affected versionversion=1ba0403ac6447f2d63914fb760c44a3b19c44eaf <fcede1f0a043ccefe9bc6ad57f12718e42f63f1d
  5. Affected versionversion=5.15.168 <5.15.177
  6. Affected versionversion=6.10.13 <6.11
  7. Affected versionversion=6.1.113 <6.1.125
  8. Affected versionversion=6.11.2 <6.12
  9. Affected versionversion=6.12
  10. Affected versionversion=63a07379fdb6c72450cb05294461c6016b8b7726 <f587c1ac68956c4703857d650d9b1cd7bb2ac4d7
  11. Affected versionversion=6.6.54 <6.6.72
  12. Affected versionversion=cae58d19121a70329cf971359e2518c93fec04fe
  13. Affected versionversion=de0456460f2abf921e356ed2bd8da87a376680bd <2550149fcdf2934155ff625d76ad4e3d4b25bbc6

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0780451f03bf518bc032a7c584de8f92e2d39d7f <be3eed59ac01f429ac10aaa46e26f653bcf581ab; version=0b8bda0ff17156cd3f60944527c9d8c9f99f1583; version=1ba0403ac6447f2d63914fb760c44a3b19c44eaf <bc2aeb35ff167e0c6b0cedf0c96a5c41e6cba1ed; version=1ba0403ac6447f2d63914fb760c44a3b19c44eaf <fcede1f0a043ccefe9bc6ad57f12718e42f63f1d; version=5.15.168 <5.15.177; version=6.10.13 <6.11; version=6.1.113 <6.1.125; version=6.11.2 <6.12; version=6.12; version=63a07379fdb6c72450cb05294461c6016b8b7726 <f587c1ac68956c4703857d650d9b1cd7bb2ac4d7; version=6.6.54 <6.6.72; version=cae58d19121a70329cf971359e2518c93fec04fe; version=de0456460f2abf921e356ed2bd8da87a376680bd <2550149fcdf2934155ff625d76ad4e3d4b25bbc6

Published CVSS scores

7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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