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...