arrow-left arrow-right autosave chat checkmark close dashboard fields fingerprint flash hamburger language list lock logotype long-arrow-right marker migrate overviews phone rocket search smiley stamp star stopwatch team twitter

Please read carefully and check if the version of your Zammad system is affected by this vulnerability. Please send information regarding vulnerabilities in Zammad to: security at zammad.com

Security Advisory Details

Vulnerability Descriptions

Authentication bypass in SSO endpoint

The SSO endpoint is used to create sessions for requests authenticated by a third party system via SSO. An attacker could send a special header to the SSO endpoint in systems that don't have SSO configured. The request would then create a valid and authenticated session that can be used to perform any actions in the name of other users. However, the user would be notified that a new device performed a login.

Special 🙏 and 🤘 and ❤️ to:

N: Dmitry Sobolev
D: Security Researcher
W: https://sobolev.com

Recommended Resolution

It's recommended to update existing Webserver/Reverse Proxies installations that can't be updated automatically.

For NginX: Extend your "server" block with "proxy_set_header X-Forwarded-User "";" as in https://github.com/zammad/zammad/blob/develop/contrib/nginx/zammad.conf

For Apache2: Extend your "VirtualHost" with "RequestHeader unset X-Forwarded-User" as in https://github.com/zammad/zammad/blob/develop/contrib/apache2/zammad_ssl.conf

This vulnerability is fixed in the latest versions of Zammad and it is recommended to upgrade to one of these.

Fixed releases can be found at:

Or just update your Zammad if installed via OS package manager.

Additional information

Online version of this advisory: https://zammad.com/news/security-advisory-zaa-2020-18

Send all remarks to security issues to security @ zammad.com.