Missing XML Validation

The software accepts XML from an untrusted source but does not validate the XML against the proper schema.


Description

Most successful attacks begin with a violation of the programmer's assumptions. By accepting an XML document without validating it against a DTD or XML schema, the programmer leaves a door open for attackers to provide unexpected, unreasonable, or malicious input.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code loads and parses an XML file.

// Read DOM
try {
  ...
  DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
  factory.setValidating( false );
  ....
  c_dom = factory.newDocumentBuilder().parse( xmlFile );
} catch(Exception ex) {
  ...
}

The XML file is loaded without validating it against a known XML Schema or DTD.

Example Two

The following code creates a DocumentBuilder object to be used in building an XML document.

DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
builderFactory.setNamespaceAware(true);
DocumentBuilder builder = builderFactory.newDocumentBuilder();

The DocumentBuilder object does not validate an XML document against a schema, making it possible to create an invalid XML document.

See Also

Data Validation Issues

Weaknesses in this category are related to a software system's components for input validation, output validation, or other kinds of validation. Validation is a freque...

SFP Secondary Cluster: Tainted Input to Command

This category identifies Software Fault Patterns (SFPs) within the Tainted Input to Command cluster (SFP24).

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses Introduced During Implementation

This view (slice) lists weaknesses that can be introduced during implementation.

Weakness Base Elements

This view (slice) displays only weakness base elements.


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