CVE-2023-0155 in Community Edition
Summary
by MITRE • 05/04/2023
An issue has been discovered in GitLab CE/EE affecting all versions before 15.8.5, 15.9.4, 15.10.1. Open redirects was possible due to framing arbitrary content on any page allowing user controlled markdown
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Analysis
by VulDB Data Team • 07/07/2025
The vulnerability identified as CVE-2023-0155 represents a critical security flaw in GitLab Community and Enterprise Edition platforms that has persisted across multiple version lines prior to specific patches. This issue manifests as an open redirect vulnerability that stems from the improper handling of user-controlled markdown content within the GitLab interface. The flaw allows malicious actors to manipulate the application's behavior by injecting crafted markdown that can redirect users to arbitrary external domains. The vulnerability specifically affects versions before 15.8.5, 15.9.4, and 15.10.1, indicating a widespread impact across the GitLab ecosystem where user-generated content processing fails to adequately validate or sanitize input before rendering.
The technical implementation of this vulnerability occurs through the markdown rendering engine's insufficient validation of URLs within user-controlled content. When GitLab processes markdown text containing links or other URL references, the system fails to properly verify that these references remain within the intended application boundaries. This weakness enables attackers to craft malicious markdown content that includes URLs pointing to external domains, potentially leading to phishing attacks or social engineering campaigns. The flaw is particularly dangerous because it leverages the legitimate markdown functionality that users expect to work normally, making the malicious behavior appear authentic and trustworthy to end users. The vulnerability falls under CWE-601, which specifically addresses open redirect vulnerabilities where web applications fail to validate redirect destinations, and aligns with ATT&CK technique T1566.001 for phishing through social engineering.
The operational impact of CVE-2023-0155 extends beyond simple redirection attacks and can enable more sophisticated exploitation patterns within GitLab environments. An attacker could craft markdown content that appears legitimate within the GitLab interface but redirects users to malicious domains when clicked, potentially compromising credentials or installing malware. The vulnerability is particularly concerning in enterprise environments where GitLab serves as a central collaboration platform for code management and project documentation. Since GitLab is widely used for hosting sensitive project information, the ability to redirect users to malicious sites through seemingly legitimate markdown content creates a significant risk for credential theft, data exfiltration, and broader security breaches. Organizations utilizing GitLab in their development workflows face potential exposure to these attacks, especially when users have access to markdown editing capabilities within project repositories or issue tracking systems.
Mitigation strategies for CVE-2023-0155 require immediate patching of affected GitLab installations to versions 15.8.5, 15.9.4, or 15.10.1, which contain the necessary fixes for the markdown validation logic. Organizations should also implement additional security controls such as content security policies that restrict external resource loading and monitor user-generated content for suspicious URL patterns. The patch addresses the core validation issue by ensuring that all URL references within markdown content are properly verified against the application's trusted domains before being rendered as clickable links. Security teams should conduct thorough audits of user permissions and access controls within GitLab to minimize the potential impact of compromised accounts. Regular security assessments of markdown processing capabilities and input validation mechanisms should be implemented as part of ongoing security monitoring efforts. The fix demonstrates the importance of proper input sanitization and the need for comprehensive validation of all user-supplied content within web applications, particularly those serving as collaborative platforms where users may have elevated privileges for content creation and modification.