CVE-2026-80844

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CVE-2026-80844

Summary: xfrm: ah6: validate routing header segments_left

Details: 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.

References: https://git.kernel.org/stable/c/0bf11081ad3753938a2b48723ce6298dbac743a1, https://git.kernel.org/stable/c/1516e31ac458a738be485620579d8f7fb2700fcb, https://git.kernel.org/stable/c/1b7e066eabcc7d6d8f476c34739b45932f2f4c31, https://git.kernel.org/stable/c/2dc650956e4e163b879b3fb1027f9557abc5c985, https://git.kernel.org/stable/c/46640c814f25f096b0b0045ca50e1b7030cd8a30, https://git.kernel.org/stable/c/48b0e36cf54358276ee7aa897034c973097d2bc9, https://git.kernel.org/stable/c/6733ae71268a27d598cfb3f3339a3c950b9b656d, https://git.kernel.org/stable/c/7bad4bda74dc4713f398d3b7624ff05478e3a568, https://git.kernel.org/stable/c/f00df8500e5a36ba70d336fd34bd2152ea074e5f, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80844.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80844, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git