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VulnerabilityPublished Updated

CVE-2025-21942: Linux kernel · btrfs: zoned: fix extent range end unlock in cow_file_range()

Affects Linux kernelSource GCVE Database

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Not known to be exploited · fixed in 6.1.191 : update Linux kernel when convenient.

Data as of 30 Oct 2026, 14:17 UTC

Severity
Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none
Patch
Available – fixed in 6.1.191

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Apr 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Linux LinuxAffected
  • =6.1.191
  • =6.6.160
Fixed in–

AI-suggested

A fix is available in Linux kernel versions 6.1.191 and 6.6.160. Users should upgrade to these or later patched versions to resolve the issue. No other mitigation is indicated or necessary as the issue is addressed by the patch.

Description

CVE-2025-21942 is a vulnerability in the Linux kernel's Btrfs filesystem zoned mode, specifically in the cow_file_range() function. The flaw causes a hang due to extent range end unlock not being properly handled when btrfs_reserve_extent() returns -EAGAIN, leading to locked extents that are never released. This results in kernel worker threads blocking indefinitely. The issue was introduced by a code change that moved unlock logic outside a loop, causing allocated extents to remain locked in certain failure cases.

References

Community reviews

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