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.
CVE-2026-86413
CVSS base score
9.1 (v3.1)
Severity
CRITICAL
Attack vector
Network
Weakness
CWE-201
Last modified
October 30, 2026
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N