XML External Entity (XXE) Injection

Affecting org.jenkins-ci.plugins:token-macro artifact, versions [,2.8)

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Overview

org.jenkins-ci.plugins:token-macro is a plugin that adds reusable macro expansion capability for other plugins to use in job configurations.

Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. A vulnerability allowed attackers able to control a the content of the input file for the "XML" macro to have Jenkins resolve external entities, resulting in the extraction of secrets from the Jenkins agent, server-side request forgery, or denial-of-service attacks.

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 org.jenkins-ci.plugins:token-macro to version 2.8 or higher.

References

CVSS Score

6.5
medium severity
  • Attack Vector
    Network
  • Attack Complexity
    High
  • Privileges Required
    None
  • User Interaction
    None
  • Scope
    Unchanged
  • Confidentiality
    High
  • Integrity
    None
  • Availability
    Low
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L
Credit
Daniel Beck, CloudBees, Inc.
CVE
CVE-2019-10337
CWE
CWE-611
Snyk ID
SNYK-JAVA-ORGJENKINSCIPLUGINS-449649
Disclosed
11 Jun, 2019
Published
12 Jun, 2019