Using various XML methods to parse untrusted XML data is known to be vulnerable to XML attacks. Using the defusedxml module is recommended. Methods should be replaced with their defusedxml equivalents.

The xml.etree.ElementTree module implements a simple and efficient API for parsing and creating XML data. But it makes the application vulnerable to:

Billion Laughs attack: It is a type of denial-of-service attack aimed at XML parsers. It uses multiple levels of nested entities. If one large entity is repeated with a couple of thousand chars repeatedly, the parser gets overwhelmed.
Quadratic blowup attack: It is similar to a Billion Laughs attack. It abuses entity expansion, too. Instead of nested entities, it repeats one large entity with a couple of thousand chars repeatedly.

Replace vulnerable imports with the equivalent defusedxml package, or make sure defusedxml.defuse_stdlib() is called.

Bad practice

import xml.etree.ElementTree as ET
tree = ET.parse('some_fie.xml') # Use of method from etree.ElementTree

Recommended

from defusedxml.ElementTree import parse
tree = parse('some_fie.xml')

References:

SonarOpenCommunity / sonar-cxx

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