CVE-2026-46193

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

xfrm: ah: account for ESN high bits in async callbacks

AH allocates its temporary auth/ICV layout differently when ESN is enabled:

the async ahash setup appends a 4-byte seqhi slot before the ICV or

auth_data area, but the async completion callbacks still reconstruct the

temporary layout as if seqhi were absent.

With an async AH implementation selected, that makes AH copy or compare

the wrong bytes on both the IPv4 and IPv6 paths. In UML repro on IPv4 AH

with ESN and forced async hmac(sha1), ping fails with 100% packet loss,

and the callback logs show the pre-fix drift:

ah4 output_done: esn=1 err=0 icv_off=20 expected_off=24

ah4 input_done: esn=1 auth_off=20 expected_auth_off=24 icv_off=32 expected_icv_off=36

Reconstruct the callback-side layout the same way the setup path built it

by skipping the ESN seqhi slot before locating the saved auth_data or ICV.

Per RFC 4302, the ESN high-order 32 bits participate in

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References