XML External Entity (XXE) Injection

Affecting de.tud.sse:soot-infoflow-android artifact, versions [,2.9.0)

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Overview

Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. This allows an attacker who has control over the source/sink definition file in XML format to read files from external locations. In order for this to occur, the XML-based format for sources and sinks has to be used and the attacker has to able control the source/sink definition file.

As a workaround, do not allow untrusted entities to control the source/sink definition file.

Details

XXE Injection is a type of attack against an application that parses XML input. XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. By default, many XML processors allow specification of an external entity, a URI that is dereferenced and evaluated during XML processing. When an XML document is being parsed, the parser can make a request and include the content at the specified URI inside of the XML document.

Attacks can include disclosing local files, which may contain sensitive data such as passwords or private user data, using file: schemes or relative paths in the system identifier.

For example, below is a sample XML document, containing an XML element- username.

<?xml version="1.0" encoding="ISO-8859-1"?>
   <username>John</username>
</xml>

An external XML entity - xxe, is defined using a system identifier and present within a DOCTYPE header. These entities can access local or remote content. For example the below code contains an external XML entity that would fetch the content of /etc/passwd and display it to the user rendered by username.

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
   <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
   <username>&xxe;</username>
</xml>

Other XXE Injection attacks can access local resources that may not stop returning data, possibly impacting application availability and leading to Denial of Service.

Remediation

Upgrade de.tud.sse:soot-infoflow-android to version 2.9.0 or higher.

References

CVSS Score

5.3
medium severity
  • Attack Vector
    Network
  • Attack Complexity
    High
  • Privileges Required
    Low
  • User Interaction
    None
  • Scope
    Unchanged
  • Confidentiality
    High
  • Integrity
    None
  • Availability
    None
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Credit
@notwo1f
CVE
CVE-2021-32754
CWE
CWE-611
Snyk ID
SNYK-JAVA-DETUDSSE-1316643
Disclosed
13 Jul, 2021
Published
13 Jul, 2021