CVE-2026-87866

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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://curl.se/docs/CVE-2026-87866.html
https://curl.se/docs/CVE-2026-87866.json
https://hackerone.com/reports/3989514
https://hackerone.com/reports/3989514

Configurations

No configuration.

History

29 Oct 2026, 19:17

Type	Values Removed	Values Added
CWE		CWE-295
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 9.1
References	~~() https://hackerone.com/reports/3989514 -~~	() https://hackerone.com/reports/3989514 -

20 Oct 2026, 21:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-20 21:17

Updated : 2026-10-29 19:17

NVD link : CVE-2026-87866

Mitre link : CVE-2026-87866

CVE.ORG link : CVE-2026-87866

JSON object : View

Products Affected

No product.

CWE

CWE-295

Improper Certificate Validation

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"references": [{"url": "https://curl.se/docs/CVE-2026-87866.html", "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://curl.se/docs/CVE-2026-87866.json", "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://hackerone.com/reports/3989514", "source": "2499f714-1537-4658-8207-48ae4bb9eae9"}, {"url": "https://hackerone.com/reports/3989514", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}], "vulnStatus": "Awaiting Analysis", "weaknesses": [{"type": "Secondary", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "description": [{"lang": "en", "value": "CWE-295"}]}], "descriptions": [{"lang": "en", "value": "When built with wolfSSL, curl can successfully validate a pinned public key\nhash against a key the TLS peer does not possess. During the TLS handshake,\nwolfSSL validates the connection, but curl's subsequent re-parsing of the same\ncertificate - tricked by a manipulated validity length field - extracts and\nmatches a different embedded key, incorrectly authorizing the pinned public\nkey."}], "lastModified": "2026-10-29T19:17:27.917", "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9"}