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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-6331

34
FAUCET Score

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.

First published: Jun 25, 2026Last modified: Jun 25, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 3.15.5, < 5.9.2CPE matchmatch criteria
cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*
>= 3.15.5, <= 5.9.1CPE match
cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

2.1LOW

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
LOCAL
Attack Complexity
HIGH
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
LOW
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.15%
Probability of exploitation in next 30 days
EPSS Percentile
4.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0015 is in the 0th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

microsoft2026-Jun/CVE-2026-6331Low

HMAC zero-length tag forgery in EVP_DigestVerifyFinal

Jun 9, 2026

References

github.com / wolfSSL/wolfssl/pull/10192
Issue TrackingPatch
wolfssl.com / docs/security-vulnerabilities
Vendor Advisory