Linux vulnerability

What happened

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 the AH ICV computation, so the async callbacks must account for the seqhi slot. Post-fix, the same IPv4 AH+ESN+forced-async-hmac(sha1) UML repro shows the corrected offset (ah4 output_done: esn=1 err=0 icv_off=24 expected_off=24) and ping succeeds; net/ipv4/ah4.o and net/ipv6/ah6.o build clean at W=1. IPv6 AH+ESN was not exercised at runtime, and the change has not been tested against a real async hardware AH engine.

Affected versions

Linux: d4d573d0334d07341beffdcf97e2b85d3955d8ae through before ec406c26c97594124e79d14516b729a8d5dced62 (git); d4d573d0334d07341beffdcf97e2b85d3955d8ae through before 1dae77078ceb4bab833f7a4935f05c5b8c97b9ba (git); d4d573d0334d07341beffdcf97e2b85d3955d8ae through before 0555d4f526232b3c9e3afbcd490c0c0793aefec6 (git); d4d573d0334d07341beffdcf97e2b85d3955d8ae through before 729899a2aa8bda7844be0cdcd3b470f11b912eda (git); d4d573d0334d07341beffdcf97e2b85d3955d8ae through before 7db99a09b3bc87268287bc7ab5f2e7f382b5ad87 (git); d4d573d0334d07341beffdcf97e2b85d3955d8ae through before 2ffaa7a94f9a4d22724364a1821735a0231d9f8d (git); d4d573d0334d07341beffdcf97e2b85d3955d8ae through before ec54093e6a8f87e800bb6aa15eb7fc1e33faa524 (git); 3.15; V3.1.6 through before * (custom) Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.