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CVE-2026-87866

9.1 · CRITICAL

When built with wolfSSL, curl can successfully validate a pinned public key hash against a key the TLS peer does not possess.

Published Oct 20, 2026CWE-295EPSS 0.51%

Overview

CVE-2026-87866 is a critical-severity vulnerability. It was published on October 20, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

When built with wolfSSL, curl can successfully validate a pinned public key

hash against a key the TLS peer does not possess. During the TLS handshake,

wolfSSL validates the connection, but curl's subsequent re-parsing of the same

certificate - tricked by a manipulated validity length field - extracts and

matches a different embedded key, incorrectly authorizing the pinned public

key.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refcurl.se/docs/CVE-2026-87866.htmlRefcurl.se/docs/CVE-2026-87866.jsonRefhackerone.com/reports/3989514Refhackerone.com/reports/3989514

How CyberStrike helps

Frequently asked questions

What is CVE-2026-87866?

CVE-2026-87866 is a critical-severity vulnerability. It was published on October 20, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-87866?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-87866?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-87866?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-87866 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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