In OpenStack Keystone before 28.0.1, the LDAP identity backend does not convert the user enabled attribute to a boolean when the user enabled invert configuration option is False (the default). The ldap res to model method in the UserApi class only performed string-to-boolean conversion when user enabled invert was True. When False, the raw string value from LDAP (e.g., "FALSE") was used directly. Since non-empty strings are truthy in Python, users marked as disabled in LDAP were treated as enabled by Keystone, allowing them to authenticate and perform actions. All deployments using the LDAP identity backend without user enabled invert=True or user enabled emulation are affected.