Docling: Unsafe XML Entity Expansion in USPTO Patent Backend

Impact

The USPTO patent XML parser used the standard xml.sax.parseString() without protection against XML External Entity (XXE) attacks. An attacker could craft malicious USPTO patent XML files with external entity references that could: - Read arbitrary files from the server filesystem - Perform Server-Side Request Forgery (SSRF) attacks - Cause denial of service through entity expansion (Billion Laughs attack)

The vulnerability affects three USPTO patent format parsers: ICE (v4.x), Grant v2.5, and Application v1.x.

Patches

Fixed in version 2.74.0. The parser now uses defusedxml.sax.make_parser() with secure configuration that blocks external entity resolution (feature_external_ges=False, feature_external_pes=False) while allowing DTD declarations required by USPTO files. This prevents XXE attacks while maintaining compatibility with the USPTO XML format.

Workarounds

Avoid processing USPTO patent XML files from untrusted sources. Implement resource limits (memory, CPU time) when processing patent documents.

### References - Fix release: v2.74.0