CVE-2025-21765 | ipv6: use RCU protection in ip6_default_advmss()

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.

Published: 2025-02-27 Last update: 2026-05-12 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-21765 is rated Low Risk (24.1/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.02%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-21765

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-30 0.05% 0.02% -0.03%
2 2025-11-13 0.05% 0.05% +0.00%
3 2025-11-04 — 0.05% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21765

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]

Weakness enumeration for CVE-2025-21765

GitHub Security Advisory for CVE-2025-21765

GHSA-cfq6-3hq6-2p95 · Severity: medium — In the Linux kernel, the following vulnerability has been resolved: ipv6: use RCU protection in...

OS Trackers for CVE-2025-21765

vendor priority summary link
debian not yet assigned CVE-2025-21765 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6. https://security-tracker.debian.org/tracker/CVE-2025-21765
redhat medium — https://access.redhat.com/security/cve/CVE-2025-21765
suse medium — https://www.suse.com/security/cve/CVE-2025-21765/
ubuntu medium CVE-2025-21765 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, released 189, ignored 154, not-affected 43, needed 20. https://ubuntu.com/security/CVE-2025-21765

Affected software / configurations for CVE-2025-21765

Vendor Product Version Raw CPE
linux linux_kernel >= 2.6.26, < 5.4.291 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.5, < 5.10.235 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.11, < 5.15.179 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.16, < 6.1.129 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.2, < 6.6.79 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.7, < 6.12.16 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.13, < 6.13.4 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel 6.14 cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:*
linux linux_kernel 6.14 cpe:2.3:o:linux:linux_kernel:6.14:rc2:*:*:*:*:*:*

References for CVE-2025-21765

URL Tags
https://git.kernel.org/stable/c/28de355b63ad42309ed5a03ee7c436c90512265b Patch
https://git.kernel.org/stable/c/3c8ffcd248da34fc41e52a46e51505900115fc2a Patch
https://git.kernel.org/stable/c/4176a68b0db8fc74ac14fcd00ba8231371051dc2 Patch
https://git.kernel.org/stable/c/550ed693f47370502a71b85382e7f9e6417300b8 Patch
https://git.kernel.org/stable/c/713a40c892f40300d63691d9f85b2a23b48fe1e8 Patch
https://git.kernel.org/stable/c/78ad057472d8c76e0602402269222f9f9c698790 Patch
https://git.kernel.org/stable/c/84212387caadb211cd9dadd6fd5563bd37dc1f5e Patch
https://git.kernel.org/stable/c/d02f30d220ef9511568a48dba8a9004c65f8d904 Patch
https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
https://cert-portal.siemens.com/productcert/html/ssa-265688.html
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