CVE-2026-46193: Linux kernel · xfrm: ah: account for ESN high bits in async callbacks
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in ec54093e6a8f87e800bb6aa15eb7fc1e33faa524 : update Linux kernel when convenient.
Data as of 6 Nov 2026, 16:34 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-06.
- Patch
- Available – fixed in ec54093e6a8f87e800bb6aa15eb7fc1e33faa524, ec406c26c97594124e79d14516b729a8d5dced62, 729899a2aa8bda7844be0cdcd3b470f11b912eda +4
Exploitation evidence
Disclosed: evidence found.
CVE published 28 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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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 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.
References
- git.kernel.org/stable/c/ec406c26c97594124e79d14516b729a8d5dced62 (opens in a new tab)
- git.kernel.org/stable/c/1dae77078ceb4bab833f7a4935f05c5b8c97b9ba (opens in a new tab)
- git.kernel.org/stable/c/0555d4f526232b3c9e3afbcd490c0c0793aefec6 (opens in a new tab)
- git.kernel.org/stable/c/729899a2aa8bda7844be0cdcd3b470f11b912eda (opens in a new tab)
- git.kernel.org/stable/c/7db99a09b3bc87268287bc7ab5f2e7f382b5ad87 (opens in a new tab)
- git.kernel.org/stable/c/2ffaa7a94f9a4d22724364a1821735a0231d9f8d (opens in a new tab)
- git.kernel.org/stable/c/ec54093e6a8f87e800bb6aa15eb7fc1e33faa524 (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)