CVE-2026-46193 is a vulnerability in Linux Kernel
Published on May 28, 2026
xfrm: ah: account for ESN high bits in async callbacks
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.
Products Associated with CVE-2026-46193
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Affected Versions
Linux:- Version d4d573d0334d07341beffdcf97e2b85d3955d8ae and below 0555d4f526232b3c9e3afbcd490c0c0793aefec6 is affected.
- Version d4d573d0334d07341beffdcf97e2b85d3955d8ae and below 729899a2aa8bda7844be0cdcd3b470f11b912eda is affected.
- Version d4d573d0334d07341beffdcf97e2b85d3955d8ae and below 7db99a09b3bc87268287bc7ab5f2e7f382b5ad87 is affected.
- Version d4d573d0334d07341beffdcf97e2b85d3955d8ae and below 2ffaa7a94f9a4d22724364a1821735a0231d9f8d is affected.
- Version d4d573d0334d07341beffdcf97e2b85d3955d8ae and below ec54093e6a8f87e800bb6aa15eb7fc1e33faa524 is affected.
- Version 3.15 is affected.
- Before 3.15 is unaffected.
- Version 6.6.140, <= 6.6.* is unaffected.
- Version 6.12.88, <= 6.12.* is unaffected.
- Version 6.18.30, <= 6.18.* is unaffected.
- Version 7.0.7, <= 7.0.* is unaffected.
- Version 7.1-rc3, <= * is unaffected.