CVE-2023-40349: Jenkins Gogs Plugin 1..15 Vulnerability Allows Unauthenticated Builds

A recently discovered vulnerability has been detected in Jenkins Gogs Plugin 1..15 and earlier versions. Identified as CVE-2023-40349, this issue can cause major problems for Jenkins users as it allows unauthenticated attackers to trigger builds of jobs. This vulnerability is in dire need of attention, as it exposes critical information and can have unsettling consequences if exploited by malicious users.

In this article, we'll dive deep into this problem, provide a code snippet to help better understand it, and finally link you to the original references to help you secure your system against potential attacks.

Vulnerability Exploit Details

The vulnerability is present in the webhook implementation within Jenkins Gogs Plugin 1..15 and earlier versions. The plugin lacks proper initialization of an option to secure its webhook endpoint, resulting in an unauthenticated attacker gaining the ability to send webhooks with arbitrary payloads. This enables the attacker to trigger the building of jobs, potentially leading to unwanted access to sensitive information, execution of commands, or worse.

Here's a code snippet showcasing this potential exploit

POST /jenkins/gogs-webhook/?job=my-super-secret-job HTTP/1.1
Host: my-jenkins-instance.com
Content-Type: application/json
Content-Length: 854

{
  "ref": "refs/heads/master",
  "before": "4e50417f658b3807e065a1391fdc8ad589d8ca43",
  "after": "211f2da490a4e55d0736bacbc8609e6237f90a",
  "compare_url": "https://fake-gogs-url.com/user/repo/compare/4e50417f658b3807e065a1391fdc8ad589d8ca43...211f2da490a4e55d0736bacbc8609e6237f90a";,
  ...
}

The above HTTP POST request illustrates how an attacker can send a forged webhook payload to the Jenkins server, triggering a build for a job named my-super-secret-job. The attacker doesn't need to provide any authentication credentials to do so.

For more details on this vulnerability, you can refer to its official sources

1. CVE Details - A technical description is available on the CVE page: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-40349
2. Jenkins Security Advisory - Get information on affected versions, related issues, and patch recommendations: https://www.jenkins.io/security/advisory/xFFS575ts/detail/CVE-2023-40349/
3. Gogs Plugin GitHub - To understand the Gogs Plugin codebase and follow the project's updates: https://github.com/jenkinsci/gogs-plugin

Solution and Recommendations

The easiest way to protect your Jenkins instance from this vulnerability is to upgrade your Jenkins Gogs Plugin to the latest version (1..16 or higher) as per the recommendations provided by the Jenkins security advisory. The latest plugin version addresses this issue and properly secures the webhook endpoint, preventing unauthenticated users from triggering jobs.

To do this, simply access the Jenkins Update Center and apply the necessary plugin updates available. In case you're unable to upgrade the plugin version, we recommend restricting access to the Jenkins webhook endpoint by placing it behind an authentication layer, such as basic access authentication or OAuth.

Additionally, it's important to monitor Jenkins logs, keep an eye on any suspicious webhook requests, and further harden the Jenkins environment to minimize the risk of exploitation.

Conclusion

CVE-2023-40349 is a severe vulnerability in Jenkins Gogs Plugin 1..15 and earlier, allowing unauthenticated attackers to trigger jobs. It's essential for Jenkins administrators to take immediate action and secure their instances against potential attacks. By upgrading to a newer version of the plugin and following the recommended best practices, you can help ensure the safety and integrity of your Jenkins environment.

Timeline

Published on: 08/16/2023 15:15:00 UTC
Last modified on: 08/18/2023 19:58:00 UTC