CVE-2025-21942

Filesystem hang via incomplete extent-range unlock

Published Apr 1, 2025 · Updated May 11, 2026

Denial of service in Linux kernel 6.13.2 through 6.13.6 allows local users to hang Btrfs filesystem workers through file I/O. In zoned mode, cow_file_range() leaves allocated extents locked after a partial allocation because the range end does not cover the allocated region. Exploitation requires a zoned Btrfs filesystem to exhaust active zones after partial allocation, leaving writeback tasks blocked on locked extents.

CVSS severity5.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux kernel 6.13.2 through 6.13.6 allows local users to hang Btrfs filesystem workers through file I/O. In zoned mode, cow_file_range() leaves allocated extents locked after a partial allocation because the range end does not cover the allocated region. Exploitation requires a zoned Btrfs filesystem to exhaust active zones after partial allocation, leaving writeback tasks blocked on locked extents.

The record

CVE
CVE-2025-21942
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-835, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=06f364284794f149d2abc167c11d556cf20c954b <5a4041f2c47247575a6c2e53ce14f7b0ac946c33
  2. Affected versionversion=10b3772292bf1be45604ba83fd9650eb94382e78 <5f4863cfb29a7b4fe7625ce148d0b9000b75b802
  3. Affected versionversion=6.13.2 <6.13.7
  4. Affected versionversion=692cf71173bb41395c855acbbbe197d3aedfa5d4 <3fcff2f55389306482ab049b4321bda49495e546

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=06f364284794f149d2abc167c11d556cf20c954b <5a4041f2c47247575a6c2e53ce14f7b0ac946c33; version=10b3772292bf1be45604ba83fd9650eb94382e78 <5f4863cfb29a7b4fe7625ce148d0b9000b75b802; version=6.13.2 <6.13.7; version=692cf71173bb41395c855acbbbe197d3aedfa5d4 <3fcff2f55389306482ab049b4321bda49495e546

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8SUSECVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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