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.
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. 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

Sun, 18 Oct 2026 14:30:00 +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. 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


cve-icon MITRE

Status: PUBLISHED

Assigner: curl

Published:

Updated: 2026-10-20T20:08:29.941Z

Reserved: 2026-09-07T12:11:55.106Z

Link: CVE-2026-86415

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-20T21:17:20.067

Modified: 2026-10-20T21:17:20.067

Link: CVE-2026-86415

cve-icon Redhat

Severity : Low

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

Links: CVE-2026-86415 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-20T23:00:23Z

Weaknesses
  • CWE-201

    Insertion of Sensitive Information Into Sent Data