CVE-2026-86413
Received Received - Intake

curl Credential Leak via Redirect in Negotiate Authentication

Publication date: 2026-10-20

Last updated on: 2026-10-20

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
2026-10-20
Generated
2026-10-21
AI Q&A
2026-10-20
EPSS Evaluated
N/A
NVD
CVE-2026-86413
EUVD
EUVD-2026-105279

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
curl curl 8.22.0
curl curl 8.21.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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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.

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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