A security vulnerability, identified as CVE-2023-4647, has been discovered in GitLab, affecting several versions of the popular web-based DevOps platform. This vulnerability specifically targets GitLab instances where the projects API pagination can be bypassed, potentially leading to denial of service (DoS) attacks. In this post, we will provide an in-depth analysis of this vulnerability, including its background, an explanation of the issue, the affected versions, a code snippet illustrating the problem, and details on the exploit.

Background

GitLab is a widely-used web-based platform designed to streamline the DevOps process by providing an array of tools for managing tasks such as source code repositories, issue tracking, and continuous deployment (CI/CD). With a large user base, the security of GitLab instances is paramount to protect valuable intellectual property, as well as ensure the stability of services hosted on the platform.

The Issue

The vulnerability - CVE-2023-4647 - in question revolves around the project's Application Programming Interface (API) pagination functionality. Pagination is utilized to efficiently manage the presentation of large datasets by breaking them down into smaller, manageable pages. In the affected GitLab versions, the pagination procedures are flawed, allowing users to tamper with and ultimately bypass the pagination controls.

This issue can expose GitLab instances to potential DoS attacks, as the bypass can cause the affected server to return an exceedingly large number of results, potentially exhausting available resources on the server and causing disruption to the platform's availability.

An example of the code illustrating the vulnerability

# Normal pagination parameters
GET /projects?page=1&per_page=100

# Malicious pagination bypass
GET /projects?page=1&per_page=-1

In this snippet, notice how the regular pagination parameters include a predefined number of items per page. The malicious request modifies the

per_page

value to a negative number (-1), allowing the bypass to occur and returning an excessive result set.

Exploit Details

To exploit this vulnerability, an attacker could craft a malicious API request, as shown in the code snippet above, by setting the per_page parameter to a negative value. This action causes the server to return all items in a single request, which could be substantial on larger GitLab instances.

If successfully conducted, this exploit could considerably disrupt the availability or performance of the affected GitLab instances, impacting other users and services.

References

For details on GitLab's official security release, please refer to their announcement here: GitLab Security Release: 16.1.5, 16.2.5, and 16.3.1

For more information on the CVE details, visit the National Vulnerability Database: CVE-2023-4647

Conclusion

This post provided a detailed analysis of the CVE-2023-4647 vulnerability present in GitLab, allowing potential DoS attacks through the projects API pagination bypass. It is crucial to ensure that your GitLab instances are updated to avoid exposure to this issue.

Timeline

Published on: 09/01/2023 11:15:00 UTC
Last modified on: 09/07/2023 20:02:00 UTC