0dd - The Zero (0) Day Division

The Zero (0) Day Division is a group of security professionals working towards a common goal; securing open-source projects.

Stroom XXE

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.

Where the Issue Occurred

The following code snippet displays the usage of XMLReader without disabling entities:

final XMLReader xmlReader = parser.getXMLReader(); 
xmlReader.setErrorHandler(new FatalErrorHandler()); 
xmlReader.parse(new InputSource(reader)); 

Source: stroom/stroom-core-server/src/main/java/stroom/entity/util/XMLUtil.java#L114-L117

Disclosure Timeline

  • Issue Reported: 23rd July 2018
  • Issue Resolved: <TBD>
  • Blog Post Published: 8th August 2018
  • Applied for CVE: 8th August 2018