CVE-2025-21766 | ipv4: use RCU protection in __ip_rt_update_pmtu()

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.

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-2025-21766 is rated Low Risk (23.6/100): 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-2025-21766

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 2026-05-10 0.05% 0.02% -0.03%
2 2025-12-24 0.04% 0.05% +0.01%
3 2025-11-21 — 0.04% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21766

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-2025-21766

GitHub Security Advisory for CVE-2025-21766

GHSA-7r26-6h4q-5x56 · Severity: medium — In the Linux kernel, the following vulnerability has been resolved: ipv4: use RCU protection in...

OS Trackers for CVE-2025-21766

vendor priority summary link
debian not yet assigned CVE-2025-21766 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 5, open 1. https://security-tracker.debian.org/tracker/CVE-2025-21766
redhat low — https://access.redhat.com/security/cve/CVE-2025-21766
suse medium — https://www.suse.com/security/cve/CVE-2025-21766/
ubuntu medium CVE-2025-21766 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 167, ignored 151, not-affected 50, needed 38. https://ubuntu.com/security/CVE-2025-21766

Affected software / configurations for CVE-2025-21766

Vendor Product Version Raw CPE
linux linux_kernel >= 4.14.200, < 4.15 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 4.19.148, < 4.20 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.4.68, < 5.5 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.8.12, < 5.9 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 5.9.1, < 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 5.9 cpe:2.3:o:linux:linux_kernel:5.9:-:*:*:*:*:*:*
linux linux_kernel 5.9 cpe:2.3:o:linux:linux_kernel:5.9:rc7:*:*:*:*:*:*
linux linux_kernel 5.9 cpe:2.3:o:linux:linux_kernel:5.9:rc8:*:*:*:*:*:*
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-2025-21766

cvelogic Threat Intelligence