CVE-2026-8720

High

Description

wc_Blake2bHmacFinal and wc_Blake2sHmacFinal discard the message when the key length exceeds the block size, producing a MAC that is independent of the input. When the supplied key is longer than the BLAKE2 block size the key-hashing branch reinitialized the running hash state, discarding the accumulated message data, so the resulting MAC depended only on the key and not on the message being authenticated. This bug is specific to the HMAC-BLAKE2 APIs that were added in wolfSSL version 5.9.0.

SeverityHigh

CVSS7.5

Exploit probability—

ProductWolfssl

PublishedJun 25, 2026

First seenJun 25, 2026

Weakness typeCWE-354CWE-354

How to fix

Update

wolfssl wolfssl5.9.2 or later

Patches

github.com/wolfSSL/wolfssl/pull/10447

Affected products

Product	Affected versions	Fixed in
wolfssl wolfssl	5.9.0 ≤ v < 5.9.2	5.9.2

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