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 …

Overview

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

• linux_kernel >= 4.11, < 5.10.258
• linux_kernel >= 5.11, < 5.15.209
• linux_kernel >= 5.16, < 6.1.175
• linux_kernel >= 6.2, < 6.6.140
• linux_kernel >= 6.7, < 6.12.86
• linux_kernel >= 6.13, < 6.18.27
• linux_kernel >= 6.19, < 7.0.4
• linux_kernel = 7.1

Remediation

Upgrade past the affected range:

• linux_kernel 7.0.4