What is CVE-2025-21765?

CVE-2025-21765 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10, affecting Linux kernel versions from 2.6.26 onward and patched in 5.4.291, 5.10.235, 5.15.179 and others. CVE-2025-21765 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2025-21765?

CVE-2025-21765 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-2025-21765?

Yes, CVE-2025-21765 has been patched. Fixed versions include 5.4.291, 5.10.235, 5.15.179 and others. If you are running Linux kernel 2.6.26 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2025-21765 actively exploited?

CVE-2025-21765 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2025-21765

Medium

In the Linux kernel, the following vulnerability has been resolved: ipv6: use RCU protection in ip6_default_advmss() ip6_default_advmss() needs 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 2.6.26 and later are affected. Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.79, 6.12.16, 6.13.4, 6.14 and their respective stable series.

Affected from

≥ 2.6.26

Fixed in

✓ 5.4.291 5.4.x ✓ 5.10.235 5.10.x ✓ 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-2025-21765 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
Debian Security
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
Cert-Portal
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
Cert-Portal
https://cert-portal.siemens.com/productcert/html/ssa-265688.html
Kernel patch commit
https://git.kernel.org/stable/c/28de355b63ad42309ed5a03ee7c436c90512265b
Patch
Kernel patch commit
https://git.kernel.org/stable/c/3c8ffcd248da34fc41e52a46e51505900115fc2a
Patch
Kernel patch commit
https://git.kernel.org/stable/c/4176a68b0db8fc74ac14fcd00ba8231371051dc2
Patch

8 patch commits total View all on NVD

Details

CVE ID CVE-2025-21765

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-2025-21765?

CVE-2025-21765 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 . It affects Linux kernel versions from 2.6.26 onward and has been patched in 5.4.291, 5.10.235, 5.15.179 and others. CVE-2025-21765 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2025-21765?

CVE-2025-21765 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-2025-21765?

Yes — CVE-2025-21765 has been patched. Fixed versions include 5.4.291, 5.10.235, 5.15.179 and others. If you are running Linux kernel 2.6.26 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2025-21765 actively exploited?

No — CVE-2025-21765 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.