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Linux vulnerability

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.

Published 27 May 2026Updated 8 Sep 202612 sources
CVSS 7.1
Overview Sources History

What happened

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.

Affected versions

Linux: f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before 77f59fb2d3aa33e90ec6cbbf45dcfb20ab82b1a9 (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before 2f31cd1e64a079c845bca31d2da7b3c90a311726 (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before d4c6a6d08e70bb1083c7c405fc7faacbf19aebc0 (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before b69933e97efea238ebbfcf70c2b1be1cd03f13e3 (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before 67f1f0933cc3d78dde222842bcad2778ec7a0b88 (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before b42821c15445f93daea3e76ada682b2b7181c476 (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before 9aff81e8217e9de2929084b03b3c7f81988c112b (git); f15f05b0a5de667c821a9727c33bce9d1d9b26dd through before 5db6ef9847717329f12c5ea8aba7e9f588a980c0 (git); 4.11; 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.

Public PoC references

No public PoC reference has passed the current publication threshold.

CorrectionsReport an issue