CVE-2023-46241

discourse-microsoft-auth is a plugin that enables authentication via Microsoft. On sites with the discourse-microsoft-auth plugin enabled, an attack can potentially take control of a victims Discourse account. Sites that have configured their applications account type to any options other than Accounts in this organizational directory only (O365 only - Single tenant) are vulnerable. This vulnerability has been patched in commit c40665f44509724b64938c85def9fb2e79f62ec8 of discourse-microsoft-auth. A microsoft_auth:revoke rake task has also been added which will deactivate and log out all users that have connected their accounts to Microsoft. User API keys as well as API keys created by those users will also be revoked. The rake task will also remove the connection records to Microsoft for those users. This will allow affected users to re-verify their account emails as well as reconnect their Discourse account to Microsoft for authentication. As a workaround, disable the discourse-microsoft-auth plugin by setting the microsoft_auth_enabled site setting to false. Run the microsoft_auth:log_out_users rake task to log out all users with associated Microsoft accounts.

Weakness

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user’s privileges and any permissions or other access-control specifications that apply to the resource. When access control checks are incorrectly applied, users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

References

• https://github.com/discourse/discourse-microsoft-auth/commit/c40665f44509724b64938c85def9fb2e79f62ec8
• https://github.com/discourse/discourse-microsoft-auth/security/advisories/GHSA-2w32-w539-3m7r
• https://learn.microsoft.com/en-us/security/zero-trust/develop/identity-supported-account-types