The Issue

An XML External Entity attack is a type of attack against an application that parses XML input. This attack occurs when XML input containing a reference to an external entity is processed by a weakly configured XML parser. This attack may lead to the disclosure of confidential data, denial of service, server side request forgery, port scanning from the perspective of the machine where the parser is located, and other system impacts.

Exist insecurely parses user-supplied XML content within the RESTServer.java file, allowing attackers to perform XXE attacks.

Where the Issue Occurred

The code below retrieves the XML content and performs insecure XML parsing (found on line 970 exist/src/org/exist/http/RESTServer.java#L970):

nsExtractor.parse(src);

The code below displays the usage within the RESTServer (found on line 318 exist/src/org/exist/http/RESTServer.java#L318)

variables = parseXML(_var, nsExtractor);

Disclosure Timeline

• Issue Reported: 29th September 2018
• Blog Post Published: 27th October 2018
• Applied for CVE: