CVE-2025-21942: Linux kernel · Infinite Loop
Source GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 29 Oct 2026, 23:17 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 1 Apr 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
- nvd.nist.gov/vuln/detail/CVE-2025-21942 (opens in a new tab)
- git.kernel.org/stable/c/3fcff2f55389306482ab049b4321bda49495e546 (opens in a new tab)
- git.kernel.org/stable/c/5a4041f2c47247575a6c2e53ce14f7b0ac946c33 (opens in a new tab)
- git.kernel.org/stable/c/5f4863cfb29a7b4fe7625ce148d0b9000b75b802 (opens in a new tab)