Synapse has improper checks for deactivated users during login
Date: 2023-06
Affected: pip/matrix-synapse
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2023-32682
CWE: CWE-287
CVSS: 5.4 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N)

### Impact It may be possible for a deactivated user to login when using uncommon configurations. This only applies if any of the following are true: * [JSON Web Tokens are enabled for login](https://matrix-org.github.io/synapse/latest/jwt.html) via the `jwt_config.enabled` configuration setting * The [local password database is enabled](https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#password_config) via the `password_config.enabled` and `password_config.localdb_enabled` configuration settings *and* a user's password is [updated via an admin API](https://matrix-org.github.io/synapse/latest/admin_api/user_admin_api.html#create-or-modify-account) after a user is deactivated. **Note that the local password database is enabled by default**, but it is uncommon to set a user's password after they've been deactivated. Installations that are configured to only allow login via Single Sign-On (SSO) via CAS, SAML or OpenID Connect (OIDC); or via an external password provider (e.g. LDAP) are not affected. ### Patches * If using JSON Web Token logins: #15624 * For other users: #15634 ### Workarounds If not using JSON Web Tokens, ensure that deactivated users do not have a password set. This list of users can be queried from PostgreSQL: ```sql SELECT name FROM users WHERE password_hash IS NOT NULL AND deactivated = 1; ```


Mitigations:

Architectural layers (MAESTRO):