CVE-2026-8720: HMAC-BLAKE2 final discards message when key length exceeds block size
wcBlake2bHmacFinal and wcBlake2sHmacFinal 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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-8720?
The severity of CVE-2026-8720 is medium with a CVSS score of 5.9.
How do I fix CVE-2026-8720?
To fix CVE-2026-8720, ensure that the key length does not exceed the block size when using HMAC-BLAKE2.
What software is affected by CVE-2026-8720?
CVE-2026-8720 affects the wolfSSL library.
What issue does CVE-2026-8720 address?
CVE-2026-8720 addresses an issue where HMAC-BLAKE2 final discards the message when the key length exceeds the block size.
When was CVE-2026-8720 published?
CVE-2026-8720 was published on June 25, 2026.