CVE-2026-6331 | HMAC zero-length tag forgery in EVP_DigestVerifyFinal, where… | CVSS 2.1 LOW

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.

Metadata

CVE ID: CVE-2026-6331
State: PUBLISHED
Assigner: wolfSSL
Reserved: 2026-04-15 03:08 UTC
Published: 2026-06-25 20:56 UTC
Last updated: 2026-06-25 20:56 UTC
Primary CWE: CWE-347
CWE-347 Improper Verification of Cryptographic Signature
Vendor / Product: wolfSSL / wolfSSL
Sources: cve.org · NVD

Severity & Metrics

2.1 LOW CVSS 4.0

CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Affected products (1)

Vendor	Product	Platform	Versions
wolfSSL	wolfSSL	—	3.15.5 ≤ 5.9.1

Weakness (CWE)

CWE	Source	Description
CWE-347	cna	CWE-347 Improper Verification of Cryptographic Signature

CVSS scores (1)

Score	Severity	Version	Source	Vector
2.1	LOW	4.0	cna	CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

References (2)