Jenkins, a widely-used open-source continuous integration and continuous delivery application, is known for its extensible nature due to the plethora of plugins available for various purposes. However, this extensibility sometimes comes at the cost of security. In this post, we will discuss the vulnerability found in the Jenkins Violations Plugin version .7.11 and earlier, which fails to prevent XML External Entity (XXE) attacks. We will cover the exploit details, and provide a code snippet along with links to original references for better understanding.

Background

The Jenkins Violations Plugin is used to parse and report on code violations found in various static code analysis tools. In version .7.11 and earlier, the plugin's XML parser is not configured correctly to guard against XXE attacks.

An XML External Entity (XXE) attack is a type of security vulnerability that allows an attacker to exploit XML parsers. XXE attacks can cause information leaks, server-side request forgery (SSRF), denial of service (DoS), remote code execution (RCE), or even complete system takeover.

Exploit Details

The vulnerability in the Jenkins Violations Plugin stems from the fact that the XML parser is not configured correctly to prevent XML External Entity (XXE) attacks. This lack of proper configuration allows an attacker to craft a malicious XML payload, which can be submitted as part of the plugin's regular operation, resulting in potentially significant security implications.

The following is a sample malicious XML payload that demonstrates the XXE vulnerability

<!DOCTYPE foo [
 <!ELEMENT foo ANY >
 <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
<violations>
 <file path="&xxe;">
 </file>
</violations>

In this example, the attacker has embedded an XXE attack within the <violations> element, which should normally contain information about code violations detected by static code analysis tools. However, the malicious payload includes an external entity reference (&xxe;) pointing to the /etc/passwd file on the host system. When the XML parser parses this payload, it will inadvertently disclose the contents of the /etc/passwd file.

Mitigation and Recommendations

To protect your Jenkins instance from this vulnerability, it is essential to upgrade the Violations plugin to version .7.12 or later. The latest version of the plugin includes a fix that properly configures the XML parser to prevent XXE attacks.

Moreover, it's essential to regularly update Jenkins as well as its plugins to ensure you're running the latest and most secure versions.

For more information about this vulnerability, the original advisory can be found here

- Jenkins Security Advisory 2022-01-18
- CVE-2022-45386 Record on MITRE

In conclusion, CVE-2022-45386 highlights the importance of ensuring that your Jenkins plugins, including the Violations Plugin, are up to date and configured correctly to prevent various security vulnerabilities like XML External Entity (XXE) attacks. By following the guidelines outlined in this post and regularly updating your systems, you can help keep your Jenkins infrastructure secure and safe from potential attackers.

Timeline

Published on: 11/15/2022 20:15:00 UTC
Last modified on: 11/18/2022 15:36:00 UTC