Vulnerability · Published Jun 25, 2026 · Assigned by wolfSSL
CVE-2026-8720HMAC-BLAKE2 final discards message when key length exceeds block size
Medium 5.9
In plain English
A medium-severity security flaw in wolfSSL from wolfSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.24 | wolfssl | 5.9.2-r0 | ALPINE-CVE-2026-8720 |
| Debian:12 | wolfssl | no fix listed | DEBIAN-CVE-2026-8720 |
| Debian:13 | wolfssl | no fix listed | DEBIAN-CVE-2026-8720 |
| Ubuntu:22.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-8720 |
| Ubuntu:24.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-8720 |
| Ubuntu:25.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-8720 |
| Ubuntu:26.04:LTS | wolfssl | no fix listed | UBUNTU-CVE-2026-8720 |
| Ubuntu:26.10 | wolfssl | no fix listed | UBUNTU-CVE-2026-8720 |
Affected products (as reported)
Weakness: CWE-354 · Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N