What is CVE-2025-21766?

CVE-2025-21766 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10, affecting Linux kernel versions from 4.14.200 onward and patched in 5.15.179, 6.1.129, 6.6.79 and others. CVE-2025-21766 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2025-21766?

CVE-2025-21766 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-2025-21766?

Yes, CVE-2025-21766 has been patched. Fixed versions include 5.15.179, 6.1.129, 6.6.79 and others. If you are running Linux kernel 4.14.200 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2025-21766 actively exploited?

CVE-2025-21766 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2025-21766

Medium

In the Linux kernel, the following vulnerability has been resolved: ipv4: use RCU protection in __ip_rt_update_pmtu() __ip_rt_update_pmtu() must use RCU protection to make sure the net structure it reads does not disappear.

Package Linux Kernel

Published 2025-02-27

Last modified 2026-05-12

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

Affected versions

Linux kernel versions 4.14.200, 4.19.148, 5.4.68, 5.8.12, 5.9 and later are affected. Fixed in 5.15.179, 6.1.129, 6.6.79, 6.12.16, 6.13.4, 6.14 and their respective stable series.

Affected from

≥ 4.14.200 ≥ 4.19.148 ≥ 5.4.68 ≥ 5.8.12 ≥ 5.9

Fixed in

✓ 5.15.179 5.15.x ✓ 6.1.129 6.1.x ✓ 6.6.79 6.6.x ✓ 6.12.16 6.12.x ✓ 6.13.4 6.13.x ✓ 6.14

References

The following references provide additional information about CVE-2025-21766 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Debian Security
https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
Cert-Portal
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
Kernel patch commit
https://git.kernel.org/stable/c/139512191bd06f1b496117c76372b2ce372c9a41
Patch
Kernel patch commit
https://git.kernel.org/stable/c/4583748b65dee4d61bd50a2214715b4237bc152a
Patch
Kernel patch commit
https://git.kernel.org/stable/c/9b1766d1ff5fe496aabe9fc5f4e34e53f35c11c4
Patch

6 patch commits total View all on NVD

Details

CVE ID CVE-2025-21766

Severity Medium

CVSS score 5.5 / 10

CVSS version 3.1

Published 2025-02-27

Modified 2026-05-12

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2025-21766?

CVE-2025-21766 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 4.14.200 onward and has been patched in 5.15.179, 6.1.129, 6.6.79 and others. CVE-2025-21766 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2025-21766?

CVE-2025-21766 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-2025-21766?

Yes — CVE-2025-21766 has been patched. Fixed versions include 5.15.179, 6.1.129, 6.6.79 and others. If you are running Linux kernel 4.14.200 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2025-21766 actively exploited?

No — CVE-2025-21766 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.