0dd - The Zero (0) Day Division

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MicroMathematics 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.

MicroMathematics parses SMathStudio files which contain XML code. This parsing is performed using an insecure XML parser.

Where the Issue Occurred

The code below retrieves the XML content and performs insecure XML parsing (found on line 179 microMathematics/app/src/main/java/com/mkulesh/micromath/io/ImportFromSMathStudio.java#L179):

final Document doc = builder.parse(stream);

Disclosure Timeline

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