CVE-2026-71403 Rancher: Identity-field mutation in /v3/users allows account hijack via principal rebind

A flaw was found in Rancher Manager. The /v3/users update path did not enforce immutability of a User resource's username and principalIds fields. A user holding the update verb on users.management.cattle.io could inject a foreign identity provider principal into any account, so that the next log...

CVE-2026-71403

CVE-2026-71403 affects Rancher Manager before version 2.15.1 . The flaw resides in the /v3/users update path, which failed to enforce immutability of the username and principalIds fields on a User resource. An attacker holding the update verb on users.management.cattle.io could inject a foreign i...