# CVE-2026-8720 — wolfSSL

> As of 2026-06-26, CVE-2026-8720 is a HIGH-severity vulnerability in wolfSSL, CVSS v3.1 7.5, EPSS 0.0% (66.2th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-8720 as of 2026-06-26; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-06-26

## 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.

The record classifies CVE-2026-8720 under weakness class [CWE-354](https://cwe.mitre.org/data/definitions/354.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 102 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **CVSS v4.0 base score:** 5.9 (`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`)
- **EPSS (FIRST):** 0.0% probability of exploitation in the next 30 days, higher than 66.2% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-06-25, last modified 2026-06-26

## Is CVE-2026-8720 being exploited?

It currently carries a trending score of 46 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [wolfSSL](https://intel.threadlinqs.com/vendors/wolfssl): wolfSSL

## How to fix CVE-2026-8720

The record marks a vendor fix as available for CVE-2026-8720. Patch reference: [https://github.com/wolfSSL/wolfssl/pull/10447](https://github.com/wolfSSL/wolfssl/pull/10447). Vendor advisory: [https://www.wolfssl.com/docs/security-vulnerabilities/](https://www.wolfssl.com/docs/security-vulnerabilities/). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-8720

No threat campaign in the Threadlinqs corpus currently references CVE-2026-8720, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, GitHub Security Advisories, FIRST EPSS. Last verified by Threadlinqs on 2026-06-28. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com — patch](https://github.com/wolfSSL/wolfssl/pull/10447)

**Other references**

- [wolfssl.com](https://www.wolfssl.com/docs/security-vulnerabilities/)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-8720
Full detection coverage and IOCs for threats exploiting CVE-2026-8720 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp