CVE-2026-8720 Details
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.
A vulnerability exists in the HMAC-BLAKE2 APIs of wolfSSL versions 5.9.0 and later, where the functions wc_Blake2bHmacFinal and wc_Blake2sHmacFinal improperly handle keys longer than the BLAKE2 block size. This oversight causes the functions to discard the message data, resulting in a MAC that relies solely on the key rather than the message being authenticated. The issue arises because the key-hashing process reinitializes the hash state, erasing the accumulated message data when a long key is supplied.
Users can update to wolfSSL version 5.9.1, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 26, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/wolfSSL/wolfssl/pull/10447 | [email protected] | Issue TrackingPatch |
| https://www.wolfssl.com/docs/security-vulnerabilities/ | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-354 | Improper Validation of Integrity Check Value | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| wolfssl wolfssl | >= 5.9.0, < 5.9.2 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 27, 2026 | Initial Analysis | [email protected] |
| Jun 26, 2026 | CVE Modified | CISA-ADP |
| Jun 25, 2026 | New CVE Received | [email protected] |