CVE-2026-86415

auto client cert connection reuse mixup

Published Oct 20, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
libcurl's connection cache match function never considers the automatic client
certificate option, so a cached, already authenticated Schannel connection can
be handed to a transfer that got redirected to a different origin, even though
the code explicitly switched off the auto client cert option for that transfer
to prevent exactly this.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics cvssV3_1

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

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Type Values Removed Values Added
Description A flaw was found in curl. In builds configured with the Microsoft Schannel Transport Layer Security (TLS) backend, libcurl's connection cache fails to evaluate client certificate authentication settings when handling HTTP redirects. A malicious server can redirect a transfer to a different destination, causing curl to inappropriately reuse an already authenticated connection. This issue can result in information disclosure by exposing client certificates and credentials to unintended origins. libcurl's connection cache match function never considers the automatic client certificate option, so a cached, already authenticated Schannel connection can be handed to a transfer that got redirected to a different origin, even though the code explicitly switched off the auto client cert option for that transfer to prevent exactly this.
Title curl: curl: auto client cert connection reuse mixup auto client cert connection reuse mixup
References
Type Values Removed Values Added
First Time appeared Curl
Curl curl
Vendors & Products Curl
Curl curl
Type Values Removed Values Added
Description A flaw was found in curl. In builds configured with the Microsoft Schannel Transport Layer Security (TLS) backend, libcurl's connection cache fails to evaluate client certificate authentication settings when handling HTTP redirects. A malicious server can redirect a transfer to a different destination, causing curl to inappropriately reuse an already authenticated connection. This issue can result in information disclosure by exposing client certificates and credentials to unintended origins.
Title curl: curl: auto client cert connection reuse mixup
Weaknesses CWE-201
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:L/I:N/A:N'}

threat_severity

Low

Weaknesses

Sources

Status
PUBLISHED
Assigner
curl
Published
Updated
Oct 30, 2026, 11:51 AM
Reserved
Sep 7, 2026, 12:11 PM
Status
Awaiting Analysis
Published
Oct 20, 2026, 9:17 PM
Modified
Oct 30, 2026, 12:16 PM
Severity
Low
Public date
Oct 14, 2026, 12:00 PM