CVE-2018-9243 in Community Edition
Summary
by MITRE
GitLab Community and Enterprise Editions version 8.4 up to 10.4 are vulnerable to XSS because a lack of input validation in the merge request component leads to cross site scripting (specifically, filenames in changes tabs of merge requests). This is fixed in 10.6.3, 10.5.7, and 10.4.7.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 02/27/2023
GitLab versions 8.4 through 10.4 contain a cross site scripting vulnerability in their merge request component that specifically affects filename handling within the changes tab interface. This vulnerability stems from insufficient input validation mechanisms that fail to properly sanitize user-supplied data before rendering it in the web interface. The flaw exists in the merge request functionality where filenames are displayed without adequate sanitization, allowing malicious actors to inject malicious scripts that execute in the context of other users' browsers. The vulnerability is categorized under CWE-79 as a failure to sanitize input data, which directly enables XSS attacks. This issue represents a significant security risk in collaborative development environments where merge requests are frequently accessed by multiple team members.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious filename containing script tags or other malicious code within the merge request changes tab. When other users view the merge request, the unsanitized filename gets rendered directly into the HTML output, causing the embedded scripts to execute in the victim's browser context. This allows attackers to potentially steal session cookies, perform actions on behalf of users, or redirect them to malicious sites. The vulnerability is particularly concerning in enterprise environments where GitLab serves as a central collaboration platform for software development teams. Attackers could leverage this flaw to escalate privileges or gain unauthorized access to sensitive code repositories and development workflows.
The operational impact of CVE-2018-9243 extends beyond simple script execution as it undermines the trust model of collaborative development platforms. In enterprise settings, this vulnerability could enable attackers to access confidential code reviews, manipulate merge request outcomes, or gain persistent access through stolen session tokens. The vulnerability affects both Community and Enterprise editions, making it widespread across organizations using GitLab. Organizations that rely on merge request workflows for code review and collaboration are particularly at risk since the attack vector is relatively simple to exploit and can be concealed within seemingly benign filenames. The fix requires updating to versions 10.6.3, 10.5.7, or 10.4.7, which implement proper input sanitization for filename display in merge request changes tabs.
Mitigation strategies should include immediate deployment of the patched versions as recommended by GitLab, along with monitoring for any suspicious activity in merge request components. Organizations should also implement additional security measures such as content security policies to limit script execution, regular security scanning of user-generated content, and user education about the risks of reviewing merge requests from untrusted sources. The vulnerability demonstrates the importance of input validation in web applications and aligns with ATT&CK technique T1213 which covers data from information repositories. Security teams should conduct thorough assessments of their GitLab installations to ensure all affected versions have been patched and implement proper access controls to limit the impact of potential exploitation. This vulnerability serves as a reminder of the critical need for robust input validation in collaborative platforms where multiple users interact with shared code repositories.