In Zammad 6.4.x before 6.4.2, there is client-side enforcement of server-side security. When changing their two factor authentication configuration, users need to re-authenticate with their current password first. However, this change was enforced in Zammad only on the front end level, and not when using the API directly.

In Zammad 6.4.x before 6.4.2, there is information exposure. Only agents should be able to see and work on shared article drafts. However, a logged in customer was able to see details about shared drafts for their customer tickets in the browser console, which may contain confidential information, and also to manipulate them via API.

Zammad before 6.4.1 places sensitive data (such as authmicrosoftoffice365credentials and applicationsecret) in log files.

In Zammad 6.4.x before 6.4.2, an authenticated agent with knowledge base permissions was able to use the Zammad API to fetch knowledge base content that they have no permission for.

In Zammad 6.4.x before 6.4.2, SSRF can occur. Authenticated admin users can enable webhooks in Zammad, which are triggered as POST requests when certain conditions are met. If a webhook endpoint returned a redirect response, Zammad would follow it automatically with another GET request. This could be abused by an attacker to cause GET requests for example in the local network.