DirtyAH6 (CVE-2026-80844)

Writeup

[!WARNING] The PoC is provided solely to help defenders, maintainers, and authorized security teams validate patches, mitigations, detections, and exposure on systems they own or are explicitly authorized to test.

You are solely responsible for ensuring that your use of this material is lawful, authorized, controlled, and conducted in an isolated test environment.

[!WARNING] This PoC is destructive. It modifies /etc/pam.d/su without any rollback. A misplaced overwrite can corrupt unrelated kernel memory and hang/crash the machine.

Run only in a disposable VM/throwaway host.

The PoC:

1. enters a private user/network namespace, builds veth, IOAM6, netem, AH6, and ESP-in-UDP paths and queues file-backed ESP skbs sourced from /etc/pam.d/su

2. sends a malformed IPv6 routing header whose segments_left exceeds its address count, making AH6 corrupt a nearby target skb

3. uses the corrupted skb metadata to make ESP decrypt chosen bytes into the file-backed PAM page, and

4. runs su - root after pam_rootok.so has become pam_permit.so.

The PoC assumes and targets x86-64 to keep things simple. In theory, the bug should not be arch-specific.

Requirements

Enumerating exhaustively for completeness:

• Fedora 43 with 7.1.3-100.fc43.x86_64, or Ubuntu 24.04 with 6.8.0-134-generic (you can try removing these checks, but other distros/kernel versions may require per-target customization/grooming)
• An ordinary non-root account and the expected, unmodified /etc/pam.d/su layout
• Unprivileged user/network namespace creation with CAP_NET_ADMIN and CAP_NET_RAW inside that namespace
• Kernel support for IPv6 AH/XFRM with HMAC-SHA256, AES-CBC ESP-in-UDP, IOAM6 LWT, sch_netem, and veth
• Misc. userspace things (which the tested distros in scope should mostly have by default): Python 3.10+, gcc, openssl, ip, tc, unshare, nsenter, su, bash, env, sh, sleep, awk, seq, grep, kill, cat, sed, rm, dd, od, and tr, plus aa-exec and the loaded trinity profile if direct unshare -Urn is denied

Fedora tested best with 16 vCPUs/32 GB RAM; Ubuntu with 29 vCPUs/8 GB RAM -- other combos might work (especially different vCPU counts). The PoC performs reasonably with a range of other vCPU/RAM combos, but YMMV.

Run it as an unprivileged user with a passwd entry.

Usage

python3 dirtyah6_root_repro.py