Skip to main content

Use Safe Defaults for `lxml` Parsers


ImportanceReview GuidanceRequires Scanning Tool
HighMerge Without ReviewNo

This codemod configures safe parameter values when initializing lxml.etree.XMLParser, lxml.etree.ETCompatXMLParser, lxml.etree.XMLTreeBuilder, or lxml.etree.XMLPullParser. If parameters resolve_entities, no_network, and dtd_validation are not set to safe values, your code may be vulnerable to entity expansion attacks and external entity (XXE) attacks.

Parameters no_network and dtd_validation have safe default values of True and False, respectively, so this codemod will set each to the default safe value if your code has assigned either to an unsafe value.

Parameter resolve_entities has an unsafe default value of True. This codemod will set resolve_entities=False if set to True or omitted.

The changes look as follows:

  import lxml.etree

- parser = lxml.etree.XMLParser()
- parser = lxml.etree.XMLParser(resolve_entities=True)
- parser = lxml.etree.XMLParser(resolve_entities=True, no_network=False, dtd_validation=True)
+ parser = lxml.etree.XMLParser(resolve_entities=False)
+ parser = lxml.etree.XMLParser(resolve_entities=False)
+ parser = lxml.etree.XMLParser(resolve_entities=False, no_network=True, dtd_validation=False)

If you have feedback on this codemod, please let us know!


Why is this codemod marked as Merge Without Review?

We believe this change is safe, effective, and protects your code against very serious security attacks.

Codemod Settings