In the Linux kernel, the Authentication Header (AH) implementation incorrectly handled the Extended Sequence Number (ESN) when operating asynchronously. The setup path inserted a 4‑byte seqhi slot but completion callbacks rebuilt the layout without accounting for it, causing the header to read or compare wrong bytes. This mismatch prevents the AH integrity check from succeeding, leading to drop of packets and, effectively, denial of service on both IPv4 and IPv6 traffic that use AH+ESN.

All systems running Linux kernel versions that enable asynchronous AH processing with ESN are affected, as identified by the CVE. The patch works for both net/ipv4/ah4.o and net/ipv6/ah6.o. Specific affected versions are not enumerated in the report, so any kernel that implements AH+ESN asynchronously and has not incorporated this fix is vulnerable.

The vulnerability is network‑based and requires the ability to send crafted AH packets with ESN to a target, which most systems can do over the public Internet or internal network. An attacker could force packet loss, disrupting connectivity without any authentication or privilege escalation. No exploit code is publicly available, and the EPSS score is not provided, but the CVE is not listed in the CISA KEV catalog. Given that the failure is tied to kernel packet processing, the impact is high for systems where AH+ESN is routinely used.