Admidio is an open-source user management solution. Prior to version 5.0.9, Role::stopMembership() does not verify whether removing a user from the administrator role leaves zero administrators. The deprecated Membership::stopMembership() contains this safety check, but the current code path bypasses it.
Any administrator can remove the last remaining other administrator, locking the entire system out of administrative access. The exploit does not require concurrent requests; sequential removals produce the same result. This issue has been patched in version 5.0.9.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
High
Admin privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
High
Complete denial of service
CVSS Vector v3.1