CVE-2018-18643 in Community Edition
Summary
by MITRE
GitLab CE & EE 11.2 and later and before 11.5.0-rc12, 11.4.6, and 11.3.10 have Persistent XSS.
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Analysis
by VulDB Data Team • 09/07/2023
GitLab CE and EE versions between 11.2 and 11.4.5, 11.3.9, and prior to 11.5.0-rc12 contain a persistent cross-site scripting vulnerability that allows attackers to inject malicious scripts into the application's user interface. This vulnerability stems from insufficient input validation and output encoding mechanisms within the GitLab platform's web application framework. The flaw enables authenticated attackers with the ability to create or modify project issues, merge requests, or comments to execute arbitrary JavaScript code in the context of other users' browsers. The vulnerability is classified under CWE-79 as a failure to sanitize user-supplied data before including it in dynamically generated web pages. This persistent nature means that the malicious scripts remain embedded within the GitLab application and execute whenever affected users view the compromised content, creating a sustained attack vector that can compromise user sessions and potentially lead to privilege escalation. The vulnerability affects the core functionality of GitLab's issue tracking and collaboration features where users can submit content that gets rendered back to other users.
The technical exploitation of CVE-2018-18643 occurs when an attacker crafts malicious input containing script tags or other XSS payloads within project issues, merge requests, or comment fields. The vulnerable GitLab versions fail to properly encode or sanitize these inputs before rendering them in the user interface, allowing the malicious scripts to execute in the browser context of other users who view the affected content. This type of vulnerability aligns with ATT&CK technique T1566.001 which covers social engineering through spearphishing with links, as attackers can craft malicious URLs or content that triggers the XSS when users navigate to specific project pages. The attack chain typically involves an attacker gaining access to a GitLab account, creating or modifying project content with malicious payloads, and then waiting for other users to view the compromised content, which then executes the attacker's code in their browsers. The vulnerability demonstrates a critical weakness in the application's security posture, particularly in its data sanitization and output encoding mechanisms that should prevent such injection attacks.
The operational impact of this vulnerability extends beyond simple script execution as it can lead to session hijacking, credential theft, and potential privilege escalation within the GitLab environment. When users with elevated privileges view malicious content, attackers can potentially escalate their privileges and gain administrative access to the GitLab instance. The persistent nature of the vulnerability means that the malicious code continues to execute for all affected users until the compromised content is removed or the GitLab instance is updated. Organizations using GitLab in production environments face significant risk as this vulnerability can be exploited by both internal and external attackers who gain access to legitimate user accounts. The vulnerability also impacts the integrity of the GitLab platform by allowing unauthorized modifications to user sessions and potentially enabling data exfiltration through the execution of malicious scripts that can access the user's browser context and communicate with external servers.
Organizations should immediately update their GitLab installations to versions 11.5.0-rc12, 11.4.6, or 11.3.10 to remediate this vulnerability. The patch addresses the root cause by implementing proper input validation and output encoding mechanisms that prevent malicious scripts from being executed in user browsers. Security teams should also implement additional monitoring and logging to detect potential exploitation attempts, particularly around project creation and modification activities. Network-based intrusion detection systems should be configured to monitor for suspicious patterns in GitLab API calls and user activities that might indicate attempted exploitation. Organizations should conduct security awareness training for developers and administrators to understand the importance of input validation and output encoding in preventing XSS vulnerabilities. The remediation process should include a comprehensive review of all user accounts for potential compromise and implementation of additional security controls such as content security policies and web application firewalls to provide defense in depth against similar vulnerabilities. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing robust input validation mechanisms in web applications.