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VulnerabilityPublished Updated

CVE-2025-21942: Linux kernel · Infinite Loop

Source GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 29 Oct 2026, 23:17 UTC

CVSS 3.1 base score
5.5Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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 29 Oct 2026.

What to do

AI-suggested

Until a fix is applied, monitoring for hung kernel worker threads related to Btrfs zoned mode and avoiding workloads triggering this condition may reduce impact.

Description

CVE-2025-21942 is a medium severity vulnerability in the Linux kernel's Btrfs filesystem zoned mode. It involves a missing unlock operation on an extent range in the cow_file_range() function, which can cause kernel worker threads to hang indefinitely. The issue arises when btrfs_reserve_extent() returns -EAGAIN due to no active zone availability, leading to a failure to unlock allocated extents properly in certain code paths. This hang can impact system availability but does not affect confidentiality or integrity.

References

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