CVE-2026-6331 Details
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.
A vulnerability exists in wolfSSL's HMAC verification process within the EVP_DigestVerifyFinal function. This issue allows a zero-length tag to be incorrectly accepted as valid during HMAC verification. The vulnerability arises because, in the OpenSSL-compatibility HMAC verify path, the length of the supplied signature was only checked to ensure it did not exceed the maximum allowed by the Message Authentication Code (MAC) length. As a result, a zero-length or truncated tag could pass verification. The vulnerability affects wolfSSL versions prior to 5.9.1.
Users are advised to update to wolfSSL version 5.9.1 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 26, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/wolfSSL/wolfssl/pull/10192 | [email protected] | Issue TrackingPatch |
| https://www.wolfssl.com/docs/security-vulnerabilities/ | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-347 | Improper Verification of Cryptographic Signature | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| wolfssl wolfssl | >= 3.15.5, < 5.9.2 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 27, 2026 | Initial Analysis | [email protected] |
| Jun 26, 2026 | CVE Modified | CISA-ADP |
| Jun 25, 2026 | New CVE Received | [email protected] |