XML External Entity (XXE) Injection Affecting com.github.binarywang:weixin-java-common package, versions [3.2.0,3.3.0)

Snyk CVSS

Attack Complexity High

Threat Intelligence

Exploit Maturity Proof of concept

EPSS 0.25% (65^th percentile)

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Snyk ID SNYK-JAVA-COMGITHUBBINARYWANG-72732
published 24 Dec 2018
disclosed 21 Dec 2018
credit 360CodeSafe

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Introduced: 21 Dec 2018

CVE-2018-20318 Open this link in a new tab CWE-611 Open this link in a new tab

How to fix?

Upgrade com.github.binarywang:weixin-java-common to version 3.3.0 or higher.

Overview

com.github.binarywang:weixin-java-common is a package that provides support for back-end development of WeChat features including WeChat payment, open platform, public number (including subscription number and service number), enterprise WeChat/enterprise number, and applet.

Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. The vulnerability can be utilised via the getXmlDoc method of the BaseWxPayResult.java 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.