How severe is CVE-2026-8720?

CVE-2026-8720 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-8720 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-8720?

CVE-2026-8720 affects Wolfssl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-8720?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-8720 have an EU (EUVD) identifier?

Yes. CVE-2026-8720 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39579.

When was CVE-2026-8720 published?

CVE-2026-8720 was published on 2026-06-25 and last updated on 2026-06-27.

CVE-2026-8720

CVE-2026-8720 is a high-severity vulnerability in Wolfssl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-354.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 5.9
EPSS exploit prediction: 0% (2nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39579
Weakness: CWE-354
Affected product: Wolfssl
Published: 2026-06-25
Last modified: 2026-06-27

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-8720?: CVE-2026-8720 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-8720 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-8720?: CVE-2026-8720 affects Wolfssl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-8720?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-8720 have an EU (EUVD) identifier?: Yes. CVE-2026-8720 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39579.
When was CVE-2026-8720 published?: CVE-2026-8720 was published on 2026-06-25 and last updated on 2026-06-27.

References

Affected products (1)

cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*

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