CVE-2026-80844 xfrm: ah6: validate routing header segments_left

What is CVE-2026-80844?

CVE-2026-80844 is a memory corruption vulnerability in Linux, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

xfrm: ah6: validate routing header segments_left

AH6 rearranges routing-header addresses before computing or verifying the ICV. ipv6_rearrange_rthdr() assumes that segments_left is not larger than the number of addresses described by the routing header's hdrlen field.

That assumption does not hold for raw IPv6 HDRINCL packets. A packet with hdrlen equal to 2 describes one address, but can carry an arbitrary segments_left value. With segments_left equal to 255, the function moves its address pointer 4,064 bytes backwards and passes a 4,064-byte length to memmove(), resulting in an out-of-bounds access.

Validate the invariant locally before modifying the routing header or performing any address-pointer arithmetic, and propagate malformed-header errors to the existing AH6 input and output error paths.

Which versions are affected by CVE-2026-80844?

How do I fix CVE-2026-80844?

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-2026-80844 being exploited?

There is no known exploitation of CVE-2026-80844 in the wild and no public exploit code.

Public exploit code: 3 proofs of concept on GitHub.

Sources

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

Also known as AZL-99411, BELL-CVE-2026-80844, DEBIAN-CVE-2026-80844, GHSA-jv4j-682x-84w7, RHSA-2026:74974, UBUNTU-CVE-2026-80844.