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LOW

CVE-2026-6331

CVE-2026-6331 — HMAC zero-length tag forgery in EVP_DigestVerifyFinal

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.

Published Updated Sources: cvelistV5, wolfSSL

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

0%

chance of exploitation in 30 days

Affects

wolfssl

wolfssl

CVSS base

2.1

LOW

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

None

none · proof-of-concept · active

Automatable

No

can an attacker script all four kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Vendors (1)

wolfssl

Products (1)

wolfssl

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactSource
2.1CVSS 4.0LOW——cvelistV5

Weakness & attack patterns

  • CWE-347

References

2 on the record

Elsewhere on this site

  • wolfsslevery CVE for this vendor
  • CWE-347other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.