CVE-2026-8720
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 5% of all known CVEs.
References
Related Vulnerabilities
Other CWE-354 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-48795 | Medium | 5.9 | 93% | - | Fix |
| CVE-2019-1166 | Medium | 5.9 | 68% | - | - |
| CVE-2024-3596 | Critical | 9.0 | 15% | - | Fix |
| CVE-2020-26141 | Medium | 6.5 | 3.1% | - | Fix |
| CVE-2020-25862 | High | 7.5 | 2.4% | - | Fix |
| CVE-2023-38802 | High | 7.5 | 1.8% | - | Fix |
Common questions
How do I fix CVE-2026-8720?
Upgrade wolfssl on debian unstable to 5.9.2-1 or later.
Is CVE-2026-8720 being actively exploited?
Not that we know of. CVE-2026-8720 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.16% is the estimated probability that it will be exploited in the next 30 days. That is higher than 5% of all scored CVEs.
How severe is CVE-2026-8720?
CVE-2026-8720 has a CVSS v3 base score of 7.5, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-8720 affect?
Published advisories record a fix for wolfssl (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-27.