Authd, through version 0.3.6, did not sufficiently randomize user IDs to prevent collisions. A local attacker who can register user names could spoof another user's ID and gain their privileges.
https://www.cve.org/CVERecord?id=CVE-2024-9312
https://github.com/ubuntu/authd/security/advisories/GHSA-4gfw-wf7c-w6g2