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Pattern: Use of insecure xml.dom.expatbuilder module

Issue: -

Description

This module is not secure against maliciously constructed data. Use defusedxml package instead.

The results of an attack on a vulnerable XML library can be fairly dramatic. With just a few hundred Bytes of XML data an attacker can occupy several Gigabytes of memory within seconds. An attacker can also keep CPUs busy for a long time with a small to medium size request. Under some circumstances it is even possible to access local files on your server, to circumvent a firewall, or to abuse services to rebound attacks to third parties.

This rule checks for the following calls:

  • xml.dom.expatbuilder.parse
  • xml.dom.expatbuilder.parseString

Example of insecure code:

import xml.dom.expatbuilder as bad

bad.parse('filethatdoesntexist.xml')
xmlString = "<note>malicious code</note>"
bad.parseString(xmlString)

Example of secure code:

import defusedxml.expatbuilder as good

good.parse('filethatdoesntexist.xml')
xmlString = "<note>malicious code</note>"
good.parseString(xmlString)

Further Reading