CVE-2026-8720

What it is

wc_Blake2bHmacFinal and wc_Blake2sHmacFinal discard the message when the key length exceeds the block size, producing a MAC that is independent of the input. When the supplied key is longer than the BLAKE2 block size the key-hashing branch reinitialized the running hash state, discarding the accumulated message data, so the resulting MAC depended only on the key and not on the message being authenticated. This bug is specific to the HMAC-BLAKE2 APIs that were added in wolfSSL version 5.9.0.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. High risk of data tampering.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-06-25 22:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-27 19:43 UTC Last updatedMost recent change to the record

Details

Published

2026-06-25 22:17 UTC

Last modified

2026-06-27 19:43 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-354

Record status

Analyzed

Affected

• Wolfssl < 5.9.2

Attack profile CVSS 4.0 · 5.9

Attack vector

Local

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

None

Integrity

High

Availability

None