Authd PAM module before version 0.3.5 can allow broker-managed users to impersonate any other user managed by the same broker and perform any PAM operation with it, including authenticating as them.
https://www.cve.org/CVERecord?id=CVE-2024-9313
https://github.com/ubuntu/authd/security/advisories/GHSA-x5q3-c8rm-w787