CVE-2025-21768: net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-27 · updated 2026-10-30
Weakness: CWE-401

Description

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels Some lwtunnels have a dst cache for post-transformation dst. If the packet destination did not change we may end up recording a reference to the lwtunnel in its own cache, and the lwtunnel state will never be freed. Discovered by the ioam6.sh test, kmemleak was recently fixed to catch per-cpu memory leaks. I'm not sure if rpl and seg6 can actually hit this, but in principle I don't see why not.

Affected products

Linux kernel: from 4.10 before 6.12.16; from 6.13 before 6.13.4; 6.14-rc1 — fixed in 6.12.16, 6.13.4
Linux: 4.10 — fixed in 6.14

How to fix

Upgrade to a fixed version: Linux kernel 6.12.16, 6.13.4; Linux 6.14. Check the vendor advisory for mitigations.

References

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