What is CVE-2026-8720?

CVE-2026-8720 is a high-severity vulnerability in Wolfssl, classified under Improper Validation of Integrity Check Value. CVSS score: 7.5/10. Published 2026-06-25.

How severe is CVE-2026-8720?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Wolfssl

CVE-2026-8720

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.

Published 2026-06-25 · last modified 2026-06-27.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.002 (4.3th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 4th percentile — 4.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Wolfssl — versions 5.9.0

Weakness classification (CWE)

CWE-354 — Improper Validation of Integrity Check Value

References

github.com/wolfSSL/wolfssl/pull/10447 (Patch, patch, Issue Tracking)
www.wolfssl.com/docs/security-vulnerabilities/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-8720?: CVE-2026-8720 is a high-severity vulnerability in Wolfssl, classified under Improper Validation of Integrity Check Value. CVSS score: 7.5/10. Published 2026-06-25.
How severe is CVE-2026-8720?: High severity. CVSS v3 base score is 7.5 out of 10.