CVE-2023-42793 - Authentication Bypass and RCE in JetBrains TeamCity Before 2023.05.4

The Common Vulnerabilities and Exposures (CVE) database, an industry-backed and highly respected register of detected security vulnerabilities in software products, has published security vulnerability CVE-2023-42793 - a critical vulnerability affecting JetBrains TeamCity.

For those unfamiliar with JetBrains TeamCity, it's an all-in-one continuous integration and continuous delivery (CI/CD) solution. TeamCity is essential for many developers around the world, as it automates the process of building, testing, and deploying software changes across various environments.

In this post, I'm going to explain CVE-2023-42793, show you how it works, and provide references to the original sources documenting this vulnerability. The vulnerability affects JetBrains TeamCity before 2023.05.4, by allowing an authentication bypass that can ultimately lead to a Remote Code Execution (RCE) attack on the TeamCity server. Keep reading to learn more about the vulnerability details, code snippets, and countermeasures to protect your infrastructure.

Vulnerability Details

CVE-2023-42793 findings reveal that an authentication bypass vulnerability exists in JetBrains TeamCity before 2023.05.4. This bypass can lead to unauthorized persons gaining access to sensitive information within your TeamCity environment, and can also elevate permissions, allowing for RCE attacks on your server.

An attacker exploiting this vulnerability could potentially execute malicious code on your server, causing severe disruptions or even compromising the integrity of your server and every project it hosts.

You can find more information about CVE-2023-42793 from the original references

1. CVE-2023-42793 entry in the CVE database: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-42793
2. Vendor security advisory: https://blog.jetbrains.com/teamcity/2023/05/teamcity-security-update-CVE-2023-42793/

Code Snippet

The following code snippet illustrates how an attacker could bypass authentication in JetBrains TeamCity before 2023.05.4, eventually getting unauthorized access to potentially sensitive information:

import requests

teamcity_url = "http://your_teamcity_url/";
api_endpoint = teamcity_url + "/httpAuth/app/rest/server?&guest=1"

response = requests.get(api_endpoint)

if response.status_code == 200:
    print("[+] Authentication bypass successful! Gained unauthorized access to TeamCity.")
else:
    print("[-] Authentication bypass failed. Please check your TeamCity URL.")

Exploiting CVE-2023-42793 usually involves a multi-step process as described below

1. Bypass the authentication mechanism in JetBrains TeamCity by taking advantage of the authentication bypass vulnerability.
2. Obtain unauthorized access to sensitive information inside your TeamCity environment, such as project configurations and settings.
3. Identify additional security weaknesses within the TeamCity environment, potentially leading to higher privileges.
4. Exploit these additional security weaknesses to execute malicious code on the server, achieving a successful RCE attack.

In order to prevent CVE-2023-42793 from affecting your TeamCity environment, follow these steps

1. Update JetBrains TeamCity to the latest version, as this issue is resolved in JetBrains TeamCity 2023.05.4 and later: https://www.jetbrains.com/teamcity/download/
2. Review your TeamCity projects and user permissions to ensure they adhere to the principle of least privilege. This can help prevent attackers from obtaining unauthorized access and potentially elevating their privileges.
3. Regularly monitor and audit access logs to detect any unauthorized access attempts. This proactive approach can help catch any attempts for exploitation at an early stage.

Conclusion

CVE-2023-42793 is a critical vulnerability that can lead to severe consequences if left unpatched in your TeamCity environment. The authentication bypass issue allows attackers to gain unauthorized access to sensitive information, potentially leading to further exploits, such as RCE. By applying the latest updates and following security best practices, you can reduce the risks associated with this vulnerability. Stay vigilant, and keep your software up-to-date.

Timeline

Published on: 09/19/2023 17:15:08 UTC
Last modified on: 10/03/2023 15:44:06 UTC