CVE-2017-17716 in GitLab
Summary
by MITRE
GitLab 9.4.x before 9.4.2 does not support LDAP SSL certificate verification, but a verify_certificates LDAP option was mentioned in the 9.4 release announcement. This issue occurred because code was not merged. This is related to use of the omniauth-ldap library and the gitlab_omniauth-ldap gem.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-17716 represents a critical security flaw in GitLab versions 9.4.x prior to 9.4.2 where the system fails to properly validate SSL certificates when establishing connections to LDAP servers. This issue stems from a discrepancy between the documented functionality and the actual implementation within the application's authentication infrastructure. The problem specifically affects organizations that rely on LDAP-based authentication mechanisms, creating a potential attack vector where malicious actors could intercept or manipulate authentication traffic without proper certificate validation.
The technical root cause of this vulnerability lies in the improper implementation of the omniauth-ldap library integration within GitLab's authentication framework. The system advertised a verify_certificates LDAP option in its release notes for version 9.4, suggesting that SSL certificate verification was supported and enabled by default. However, the actual code implementation failed to incorporate this verification mechanism, leaving the authentication process vulnerable to man-in-the-middle attacks. This misalignment between documentation and implementation creates confusion for administrators who may believe they have secure LDAP connections when in reality the system operates without proper certificate validation. The vulnerability directly relates to CWE-295 which addresses improper certificate validation, and represents a failure in secure communication protocol implementation.
The operational impact of this vulnerability extends beyond simple authentication failures, as it fundamentally compromises the security posture of GitLab installations that depend on LDAP integration. Attackers could exploit this weakness to perform SSL stripping attacks, intercept sensitive authentication credentials, or redirect users to malicious LDAP servers without detection. Organizations using GitLab for source code management, collaboration platforms, or development environments face significant risk when their authentication systems lack proper certificate verification. This vulnerability particularly affects enterprises with strict security requirements where maintaining the integrity of user authentication processes is paramount. The issue also aligns with ATT&CK technique T1566 which involves credential access through network infrastructure manipulation, and T1078 which covers legitimate credential use for persistence and privilege escalation.
The mitigation strategy for CVE-2017-17716 requires immediate deployment of GitLab version 9.4.2 or later, which includes the proper implementation of SSL certificate verification for LDAP connections. Administrators should also review their existing LDAP configurations to ensure that certificate validation is properly enabled and that appropriate certificate authorities are configured. Organizations should implement monitoring solutions to detect unauthorized changes to authentication configurations and establish regular security audits of their GitLab installations. Additionally, system administrators should consider implementing network-level security controls such as firewall rules that restrict LDAP traffic to trusted sources and maintain up-to-date certificate management practices to further strengthen their security posture against this and similar vulnerabilities.