CVE-2026-8720: HMAC-BLAKE2 final discards message when key length exceeds block size
CSIRTS triage
- What
- HMAC-BLAKE2 final discards the message when the key length exceeds the block size.
- Who is affected
- Users of OpenSSL that implement HMAC-BLAKE2 with long keys.
- Urgency
- This is a high severity issue that should be remediated promptly to ensure data integrity.
- Action
- Update to the latest version of OpenSSL.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-8720
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-87200.11% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-8720 | coverage & exploitation status | NVD · CVE.org |
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