OWASP Periodic Table of Vulnerabilities - XML External Entities

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XML External Entities

Root Cause Summary

The XML parser is configured to process an unsafe DTD which includes external references to resources on the filesystem or other internal resources.

Browser / Standards Solution

None

Perimeter Solution

None

Generic Framework Solution

Disable external entity processing in the XML parser. Use strict, static, internally-defined DTDs and discard DTDs defined by XML documents. Force the application to load external content safely using framework file access code, instead of delegating the work to the XML parser.

Custom Framework Solution

None

Custom Code Solution

None

Discussion / Controversy

XXE is an unsafe development pattern and should be discarded in favor of safer methods of building documents from multiple sources.

References

XML External Entity Processing
XML External Entity (XXE) Prevention Cheat Sheet
XML External Entities (WASC)
CWE-611: Improper Restriction of XML External Entity Reference ('XXE')