CVE-2026-87866
Full vulnerability record from the local CVENow database.
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.
Severity
CRITICAL
CVSS score
9.1
(v3.1)
Vulnerability status
Awaiting Analysis
Source identifier
2499f714-1537-4658-8207-48ae4bb9eae9
Published
2026-10-20 21:17:20.833000
Last modified
2026-10-29 19:17:27.917000
View original CVE JSON
{
"id": "CVE-2026-87866",
"sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9",
"published": "2026-10-20T21:17:20.833",
"lastModified": "2026-10-29T19:17:27.917",
"vulnStatus": "Awaiting Analysis",
"cveTags": [],
"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."
}
],
"affected": [
{
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"affectedData": [
{
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],
"metrics": {
"cvssMetricV31": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary",
"cvssData": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"attackVector": "NETWORK",
"attackComplexity": "LOW",
"privilegesRequired": "NONE",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"availabilityImpact": "NONE"
},
"exploitabilityScore": 3.9,
"impactScore": 5.2
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-10-29T18:58:30.759022Z",
"id": "CVE-2026-87866",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "yes"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"weaknesses": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-295"
}
]
}
],
"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"
}
]
}