Zimbra Collaboration XXE

Zimbra Collaboration Suite is a groupware suite that comprises an email server and a web client. It holds a server-side request forgery vulnerability and an XML external entity vulnerability. This can lead to remote code execution. XML external entity vulnerability is found in Autodiscover Servelet which helps to read the Zimbra configuration file. This configuration file contains an LDAP password for the Zimbra account which on exploitation helps the attacker to get the user authentication cookie along with an AuthRequest message. The authentication cookie can then be used server-side request forgery.The forgery can be carried out in the Proxy Servlet, where the attacker can send a proxy AuthRequest to the admin port along with the credentials to obtain the admin cookie. To start the remote code execution, the attacker uses the Client Upload servlet to upload a JSP webshell which might be triggered from the webserver. This exploit is applicable for Zimbra Collaboration Suite v8.5 to v8.7.11.

Mitigation / Precaution

In order to patch this vulnerability, please install the official patch Zimbra made available for supported, vulnerable instances.

Written by

Jijith Rajan

Cyber Security Engineer