DDFFileParser is vulnerable to XXE Attacks

Impact

DDFFileParser and DefaultDDFFileValidator (and so ObjectLoader) are vulnerable to XXE Attacks.

DDF file is a LWM2M format used to store LWM2M object description.
Leshan users are impacted only if they parse untrusted DDF files (e.g. if they let external users provide their own model), in that case they MUST upgrade to fixed version.
If you parse only trusted DDF file and validate only with trusted xml schema, upgrading is not mandatory.

Patches

This is fixed in v1.5.0 and2.0.0-M13.

Workarounds

No easy way. Eventually writing your own DDFFileParser/DefaultDDFFileValidator (and so ObjectLoader) creating a DocumentBuilderFactory with :

// For DDFFileParser
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true); // Disable DTDs
factory.setXIncludeAware(false); // Disable XML Inclusions
factory.setExpandEntityReferences(false); // disable expand entity reference nodes

// For DefaultDDFFileValidator
SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
factory.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, "");
factory.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, "");

References

• https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing
• https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html
• https://semgrep.dev/docs/cheat-sheets/java-xxe/
• https://community.veracode.com/s/article/Java-Remediation-Guidance-for-XXE