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.
Published: 2026-10-20
Score: 3.7 Low
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories

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History

Tue, 20 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Description A flaw was found in curl. This vulnerability allows a malicious server to bypass public key pinning when curl is built with the wolfSSL backend. By presenting a specially crafted certificate with a manipulated validity length field, the attacker can trick curl into improperly re-parsing the certificate and authorizing an invalid key during the Transport Layer Security (TLS) handshake. 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.
Title curl: curl: wolfSSL public-key pinning bypass wolfSSL public-key pinning bypass
References

Sun, 18 Oct 2026 15:00:00 +0000

Type Values Removed Values Added
First Time appeared Curl
Curl curl
Vendors & Products Curl
Curl curl

Sat, 17 Oct 2026 00:30:00 +0000

Type Values Removed Values Added
Description A flaw was found in curl. This vulnerability allows a malicious server to bypass public key pinning when curl is built with the wolfSSL backend. By presenting a specially crafted certificate with a manipulated validity length field, the attacker can trick curl into improperly re-parsing the certificate and authorizing an invalid key during the Transport Layer Security (TLS) handshake.
Title curl: curl: wolfSSL public-key pinning bypass
Weaknesses CWE-295
References
Metrics threat_severity

None

 cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N'}

threat_severity

Low

Subscriptions

Curl Curl
cve-icon MITRE

Status: PUBLISHED

Assigner: curl

Published:

Updated: 2026-10-20T20:16:30.866Z

Reserved: 2026-09-09T13:17:42.764Z

Link: CVE-2026-87866

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-20T21:17:20.833

Modified: 2026-10-22T17:21:57.293

Link: CVE-2026-87866

cve-icon Redhat

Severity : Low

Publid Date: 2026-10-14T12:00:00Z

Links: CVE-2026-87866 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-20T22:15:07Z

Weaknesses