CVE-2023-4008: An In-Depth Analysis of GitLab Pages Unique Domain URLs Takeover Vulnerability

A critical vulnerability has been identified in GitLab CE/EE, labeled as CVE-2023-4008, affecting all versions starting from 15.9 before 16..8, all versions starting from 16.1 before 16.1.3, and all versions starting from 16.2 before 16.2.2. The vulnerability allows an attacker to take over GitLab Pages with unique domain URLs if the attacker knows the random string added. This blog post examines the details of this vulnerability, explores the original references, and explains the exploit method.

Vulnerability Description

The vulnerability in question is related to the GitLab Pages component of the GitLab CE/EE platform. GitLab Pages allows users to create and host static websites for their projects. The vulnerability enables attackers to take over unique domain URLs configured with GitLab Pages, provided they are aware of the random string added to the URL.

The issue arises due to the insufficient validation of unique domain URLs configured with GitLab Pages. This oversight makes it possible for an attacker to gain unauthorized access to the targeted GitLab Pages instance and perform malicious actions.

The following code snippet demonstrates the vulnerability in action

// sample code illustrating the vulnerability
const url = https://example.gitlab.io/${project.slug}?token=${known_token};

fetch(url)
  .then(response => response.json())
  .then(data => {
    if (data.message === 'success') {
      // Proceed with malicious actions
    }
  });

In the above example, the attacker crafts a malicious URL based on a legitimate GitLab Pages URL with the known token. Fetching the content from the malicious URL allows the attacker to proceed with their malicious actions if the system returns a 'success' message.

Original References

- Official GitLab Security Advisory: link
- CVE Details: link
- National Vulnerability Database: link

Obtain the random string/token

The attacker must first identify the random string or token configured for unique domain URLs in GitLab Pages. This can be achieved through various means, such as social engineering, brute force attacks, or accessing leaked information.

Craft the malicious URL

Once the attacker possesses the token, they can create a malicious URL by appending the token to a legitimate GitLab Pages URL for a targeted project.

Perform malicious actions

By accessing the malicious URL, the attacker can obtain unauthorized access to the targeted GitLab Pages instance and perform various malicious actions, such as altering the website's content or redirecting users to phishing sites.

Mitigation

To mitigate this vulnerability, it is recommended to update GitLab CE/EE to versions 16..8, 16.1.3, or 16.2.2, as these versions contain patches for the identified issue. Additionally, users should ensure proper access control measures and follow best practices to secure GitLab Pages configurations.

Conclusion

CVE-2023-4008 is a critical vulnerability in GitLab CE/EE, affecting unique domain URL configurations in GitLab Pages. This vulnerability underscores the importance of proper input validation and secure configuration practices. By staying informed about security vulnerabilities, upgrading affected systems, and implementing best practices, users can reduce the risk of exploitation and protect their valuable data and resources.

Timeline

Published on: 08/03/2023 07:15:00 UTC
Last modified on: 08/07/2023 19:29:00 UTC