CVE-2026-86413

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curl Credential Leak via Redirect in Negotiate Authentication

Publication date: 2026-10-20

Last updated on: 2026-10-30

Assigner: curl

Description

When using an *ambient user* in a first transfer doing Negotiate authentication and asked to follow redirects, curl could pass on its credential details to an unrelated second origin when asked to redirect there.

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Meta Information

Published

2026-10-20

Last Modified

2026-10-30

Generated

2026-11-10

AI Q&A

2026-10-20

EPSS Evaluated

2026-11-08

NVD

CVE-2026-86413

EUVD

EUVD-2026-105279

Affected Vendors & Products

Vendor	Product	Version / Range
curl	curl	8.22.0
curl	curl	8.21.0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-201	The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.

Attack-Flow Graph

Executive Summary

This vulnerability in curl occurs during a transfer using Negotiate authentication with an ambient user. When curl follows redirects, it may pass on credential details to a second, unrelated origin. This happens because curl forwards credentials to the new destination even if it is a different origin.

Detection Guidance

To detect this vulnerability, check if your system is running curl versions 8.21.0 through 8.22.0. Run 'curl --version' to verify the version. If using Negotiate authentication with ambient users and redirects, monitor network traffic for credential exposure during redirects.

Impact Analysis

The impact is credential leakage during HTTP redirects when Negotiate authentication is used. Attackers could intercept credentials sent to unintended destinations, potentially leading to unauthorized access to sensitive resources.

Compliance Impact

This vulnerability could lead to unintended credential exposure during HTTP redirects when Negotiate authentication is used. This may violate data protection principles under GDPR and HIPAA, which require safeguarding sensitive authentication credentials and preventing unauthorized access to personal or health data.

Mitigation Strategies

Upgrade curl to version 8.23.0 or later. Alternatively, avoid using ambient users with Negotiate authentication or configure curl to disallow usernames in URLs. Apply patches if upgrading is not immediately possible.

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