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VulnerabilityCVE-2026-6331Published 2026-06-25

CVE-2026-6331 — wolfSSL

low (derived)

As of 2026-06-26, CVE-2026-6331 is a Low-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in wolfSSL, CVSS v4.0 2.1, EPSS 0.1% (1.0th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-6331 as of 2026-06-26; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

CVSS v4.0
2.1/10Low (derived)
EPSS
0.1%Higher than 1.0% of scored CVEs
CISA KEV
NoNot in the KEV catalog
Tracked threats
0None linked yet
Priority
1.1/10Threadlinqs triage score
Published
Updated 2026-06-26
CVSS v4.0 2.1 (Low, derived from score) · EPSS 0.1% (higher than 1.0% of all scored CVEs) · Priority 1.1/10 · Published 2026-06-25

Last updated:

What is CVE-2026-6331?

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.

The record classifies CVE-2026-6331 under weakness class CWE-347. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 102 days ago.

Severity and exploitation probability

CVSS v4.0 base score
2.1 — Low (derived from score)
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
EPSS (FIRST)
0.1% probability of exploitation in the next 30 days, higher than 1.0% of all scored CVEs
CISA KEV
Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority
1.1/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published
2026-06-25, last modified 2026-06-26

Is CVE-2026-6331 being exploited?

It currently carries a trending score of 30 in the Threadlinqs vulnerability feed.

Affected products and versions

How to fix CVE-2026-6331

No vendor patch reference has been recorded for CVE-2026-6331 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-6331

No threat campaign in the Threadlinqs corpus currently references CVE-2026-6331, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

Other references