CVE-2018-17536 in Community Edition
Summary
by MITRE • 04/16/2023
An issue was discovered in GitLab Community and Enterprise Edition before 11.1.7, 11.2.x before 11.2.4, and 11.3.x before 11.3.1. There is stored XSS on the merge request page via project import.
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Analysis
by VulDB Data Team • 05/05/2023
This vulnerability represents a critical stored cross-site scripting flaw in GitLab's merge request functionality that affects multiple versions of the popular DevOps platform. The issue stems from inadequate input validation and output encoding mechanisms when processing project import operations, allowing attackers to inject malicious JavaScript code that persists within the merge request pages. The vulnerability specifically targets the project import feature which enables users to import repositories from various sources including external Git servers, making it a significant vector for attack exploitation. The stored nature of this XSS vulnerability means that malicious code injected during the import process remains persistent in the system and executes whenever users view affected merge request pages, creating a sustained threat vector that can compromise user sessions and access credentials.
The technical implementation of this vulnerability involves the failure to properly sanitize user-supplied data during the project import process, particularly when handling repository metadata and commit information. When GitLab processes imported projects, it does not adequately escape or encode special characters in the imported data before storing it in the database and subsequently rendering it on merge request pages. This creates an environment where attackers can craft malicious import payloads containing JavaScript code that executes in the context of other users' browsers. The vulnerability affects both Community and Enterprise editions of GitLab, with specific version ranges indicating that the fix was implemented in releases 11.1.7, 11.2.4, and 11.3.1, suggesting that the issue was present across a significant portion of GitLab's 11.x release cycle. The flaw directly maps to CWE-79 which defines cross-site scripting vulnerabilities as weaknesses that occur when an application includes untrusted data in a web page without proper validation or escaping.
From an operational perspective, this vulnerability poses substantial risk to organizations using GitLab as their primary code repository and collaboration platform. Attackers could exploit this vulnerability to steal session cookies, perform unauthorized actions on behalf of users, redirect victims to malicious sites, or even escalate privileges within the GitLab environment. The impact extends beyond individual user compromise to potentially affect entire development teams and organizational security postures, especially in environments where GitLab serves as the central hub for code review and collaboration processes. The merge request page represents a high-traffic area where developers frequently access information, making it an ideal target for persistent XSS attacks that could remain undetected for extended periods. Security teams would face challenges in detecting such attacks since the malicious code executes within legitimate user sessions and appears to originate from trusted GitLab infrastructure.
The exploitation of this vulnerability aligns with several techniques documented in the attack framework including those targeting web application vulnerabilities and session hijacking methods. Attackers could leverage this flaw to create malicious merge requests that automatically execute scripts when viewed by other team members, potentially leading to credential theft or privilege escalation. The vulnerability also demonstrates the importance of proper input validation and output encoding practices in web applications, particularly in collaborative platforms where user-generated content is extensively processed and displayed. Organizations should implement immediate mitigations including upgrading to patched versions of GitLab, implementing web application firewalls, and conducting security reviews of imported projects. The incident highlights the critical need for comprehensive security testing of import and export functionality in development platforms, as these features often receive less scrutiny than core application components. Additionally, this vulnerability underscores the necessity of maintaining current security patches and implementing automated vulnerability scanning processes to identify and remediate similar issues before they can be exploited in production environments.