What is CVE-2025-21900?

CVE-2025-21900 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10, classified as a Improper Locking flaw (CWE-667), affecting Linux kernel versions from 6.11 onward and patched in 6.12.18, 6.13.6 and 6.14. CVE-2025-21900 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2025-21900?

CVE-2025-21900 has a CVSS score of 5.5 out of 10, rated Medium severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Is there a patch available for CVE-2025-21900?

Yes, CVE-2025-21900 has been patched. Fixed versions include 6.12.18, 6.13.6 and 6.14. If you are running Linux kernel 6.11 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2025-21900 actively exploited?

CVE-2025-21900 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is Improper Locking (CWE-667)?

The product does not properly acquire or release a lock, which can lead to unexpected behaviour. See MITRE CWE for full details: https://cwe.mitre.org/data/definitions/667.html

CVE-2025-21900

Medium

In the Linux kernel, the following vulnerability has been resolved: NFSv4: Fix a deadlock when recovering state on a sillyrenamed file If the file is sillyrenamed, and slated for delete on close, it is possible for a server reboot to triggeer an open reclaim, with can again race with the application call to close(). When that happens, the call to put_nfs_open_context() can trigger a synchronous delegreturn call which deadlocks because it is not marked as privileged. Instead, ensure that the call to nfs4_inode_return_delegation_on_close() catches the delegreturn, and schedules it asynchronously.

Package Linux Kernel

Published 2025-04-01

Last modified 2025-10-01

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

5.5

out of 10

Medium

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

High

Vector string

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

Weakness type

CWE-667

CVE-2025-21900 is a Improper Locking vulnerability

What is Improper Locking?

The product does not properly acquire or release a lock, which can lead to unexpected behaviour. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.11 and later are affected. Fixed in 6.12.18, 6.13.6, 6.14 and their respective stable series.

Affected from

≥ 6.11

Fixed in

✓ 6.12.18 6.12.x ✓ 6.13.6 6.13.x ✓ 6.14

References

The following references provide additional information about CVE-2025-21900 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Kernel patch commit
https://git.kernel.org/stable/c/4fe4ae6c2e01d028856b73b6328b12b8945df871
Patch
Kernel patch commit
https://git.kernel.org/stable/c/8f8df955f078e1a023ee55161935000a67651f38
Patch
Kernel patch commit
https://git.kernel.org/stable/c/f41a60bc43e7abbc636fee78bed0d74c31e738b0
Patch

Details

CVE ID CVE-2025-21900

Severity Medium

CVSS score 5.5 / 10

CVSS version 3.1

Published 2025-04-01

Modified 2025-10-01

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2025-21900?

CVE-2025-21900 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 , classified as an Improper Locking flaw (CWE-667) . It affects Linux kernel versions from 6.11 onward and has been patched in 6.12.18, 6.13.6 and 6.14. CVE-2025-21900 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2025-21900?

CVE-2025-21900 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
Is there a patch available for CVE-2025-21900?

Yes — CVE-2025-21900 has been patched. Fixed versions include 6.12.18, 6.13.6 and 6.14. If you are running Linux kernel 6.11 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2025-21900 actively exploited?

No — CVE-2025-21900 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.
What is Improper Locking (CWE-667)?

The product does not properly acquire or release a lock, which can lead to unexpected behaviour. View CWE-667 on MITRE CWE →