CVE-2026-6331

High

Description

HMAC zero-length tag forgery in EVP_DigestVerifyFinal, where a zero-length tag could be accepted as valid during HMAC verification. In the OpenSSL-compatibility HMAC verify path the supplied signature length was only checked as not exceeding the MAC length, so a zero-length or otherwise truncated tag could pass verification. The fix requires the supplied tag length to exactly equal the MAC length and rejects a zero-length MAC, so a forged short or empty tag is no longer accepted.

SeverityHigh

CVSS7.5

Exploit probability—

ProductWolfssl

PublishedJun 25, 2026

First seenJun 25, 2026

Weakness typeCWE-347CWE-347

How to fix

Update

wolfssl wolfssl5.9.2 or later

Patches

github.com/wolfSSL/wolfssl/pull/10192

Affected products

Product	Affected versions	Fixed in
wolfssl wolfssl	3.15.5 ≤ v < 5.9.2	5.9.2

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