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CVE-2023-5356: GitLab CE/EE Incorrect Authorization Check that Enables Unauthorized Slash Command Execution

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Overview

CVE-2023-5356 is a severe vulnerability affecting GitLab Community Edition (CE) and Enterprise Edition (EE), which may lead to unauthorized command execution and potential system compromise. It arises from improper authorization checks in multiple versions of GitLab CE/EE, allowing users to exploit slack/mattermost integrations and execute slash commands as different users. This vulnerability is critical as it could lead to data leakage or complete system compromise if exploited.

Vulnerability Summary

CVE ID: CVE-2023-5356
Severity: High (CVSS: 7.3)
Attack Vector: Network
Privileges Required: Low
User Interaction: Required
Impact: Unauthorized command execution as a different user leading to potential system compromise or data leakage

Affected Products

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Product | Affected Versions

GitLab CE/EE | 8.13 to 16.5.5
GitLab CE/EE | 16.6 to 16.6.3
GitLab CE/EE | 16.7 to 16.7.1

How the Exploit Works

The exploit works by abusing the slack/mattermost integrations in GitLab, enabling a user to execute slash commands as another user. This is due to incorrect authorization checks within these versions of GitLab, which fail to properly validate the user executing the commands. Essentially, an attacker could manipulate the communication between GitLab and the slack/mattermost platforms to execute potentially malicious commands.

Conceptual Example Code

Here’s a conceptual example of how this vulnerability might be exploited using an HTTP request:

POST /api/v4/projects/:id/services/slack/slash_commands HTTP/1.1
Host: GitLab.example.com
Content-Type: application/json
{
"token": "slack_token",
"user_id": "malicious_user",
"command": "/execute",
"text": "malicious_command"
}

In this example, a malicious user sends a POST request to the slack slash commands service on the GitLab server, executing a potentially harmful command under the guise of another user.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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