CVE-2026-6331

HMAC zero-length tag forgery in EVP_DigestVerifyFinal

Published Jun 25, 2026 CVSS 4.0 · 2.1 Low EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4683-1 wolfssl security update
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Wolfssl
Wolfssl wolfssl
Vendors & Products Wolfssl
Wolfssl wolfssl
Type Values Removed Values Added
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.
Title HMAC zero-length tag forgery in EVP_DigestVerifyFinal
Weaknesses CWE-347
References
Metrics cvssV4_0

{'score': 2.1, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
wolfSSL
Published
Updated
Jun 26, 2026, 1:53 PM
Reserved
Apr 15, 2026, 3:08 AM
Status
Analyzed
Published
Jun 25, 2026, 10:17 PM
Modified
Jun 27, 2026, 7:48 PM