CVE-2026-80844
xfrm: ah6: validate routing header segments_left
- Published
- Sep 4, 2026
- Updated
- Sep 4, 2026
- Assigning CNA
- Linux
- Evidence observed
- Sep 18, 2026
Low · next 30 days
- Percentile
- 9.5%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
3Research repository for CVE-2026-80844 (DirtyAH6), a Linux kernel IPv6 AH6/XFRM local privilege escalation, with PoC, root-cause and patch analysis.
- DirtyAH6PoC
Python PoC for CVE-2026-80844: IPv6 AH6 skb corruption and ESP-in-UDP decryption to overwrite /etc/pam.d/su and escalate to root on Linux.
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