CVE-2026-8720
HMAC-BLAKE2 final discards message when key length exceeds block size
Description
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.
INFO
Published Date :
June 25, 2026, 9:18 p.m.
Last Modified :
June 25, 2026, 9:18 p.m.
Remotely Exploit :
No
Source :
wolfSSL
Affected Products
The following products are affected by CVE-2026-8720
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | 50d2cd11-d01a-48ed-9441-5bfce9d63b27 |
Solution
- Downgrade wolfSSL to a version before 5.9.0.
- Verify HMAC-BLAKE2 functionality with the downgrade.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-8720 vulnerability anywhere in the article.