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

What is CVE-2025-21768?

CVE-2025-21768 is a medium-severity memory corruption vulnerability in Linux kernel, published on 27 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Weakness: CWE-401

Which versions are affected by CVE-2025-21768?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21768?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2025-21768 being exploited?

There is no known exploitation of CVE-2025-21768 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-62544, AZL-68979, BELL-CVE-2025-21768, DEBIAN-CVE-2025-21768, GHSA-r5gw-qwwg-wx9p, ROOT-OS-DEBIAN-11-CVE-2025-21768 and 4 more.