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Overview of the Vulnerability

GitLab’s recent critical security release addresses a vulnerability identified as CVE-2023-5009. This vulnerability, with a CVSS score of 9.6, posed a significant risk, particularly in the pipeline execution processes of GitLab’s software. It affected versions before 16.2.7 of GitLab Enterprise Edition (EE) and versions before 16.3.4 of GitLab Community Edition (CE).

Technical Analysis of the Vulnerability

The CVE-2023-5009 vulnerability is notable for allowing an attacker to execute pipelines as another user, compromising the security of the projects hosted on GitLab. This flaw was a bypass of the earlier CVE-2023-3932 vulnerability.

Exploitation Technique: Parameter Pollution

The vulnerability could be exploited using a technique known as parameter pollution. Here’s an illustrative example to demonstrate how an attacker might craft a malicious request:

POST /users/password HTTP/2


… [additional request headers] …

Content-Type: application/x-www-form-urlencoded

authenticity_token=readactd&user[email][][email protected]&user[email][][email protected]

In this hypothetical example, the attacker uses the user[email][] parameter multiple times, leading to an ambiguity in the request processing. This kind of exploitation could allow unauthorized access to Gitlab projects with exploited user permissions.

Mitigation and Patching

GitLab has released patches in the latest versions — 16.3.4 for Community Edition and 16.2.7 for Enterprise Edition. Users are strongly advised to upgrade to these versions for immediate mitigation.

For Older Versions

If you are using a version prior to 16.2, there are additional considerations. The vulnerability is active only if both ‘Direct Transfers’ and ‘Security Policies’ features are enabled. As a workaround, disabling one or both of these features can mitigate the risk.

Additional Updates in the Patch

Besides the critical security fixes, the new versions of GitLab also include other non-security related improvements, such as a new indexer in version 16.3.4 and minor feature reversions in 16.2.7.

Final Recommendations

Given the severity and the potential impact of CVE-2023-5009, it is imperative for users and administrators of GitLab to update their instances to the latest versions as a priority. This action not only resolves the highlighted flaw but also fortifies the overall security posture against similar vulnerabilities in the future​​​​.

More details on CVE-2023-5009 – Learn more.

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