CVE-2023-6680 in Enterprise Edition
Summary
by MITRE • 12/15/2023
An improper certificate validation issue in Smartcard authentication in GitLab EE affecting all versions from 11.6 prior to 16.4.4, 16.5 prior to 16.5.4, and 16.6 prior to 16.6.2 allows an attacker to authenticate as another user given their public key if they use Smartcard authentication. Smartcard authentication is an experimental feature and has to be manually enabled by an administrator.
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Analysis
by VulDB Data Team • 12/15/2023
The vulnerability CVE-2023-6680 represents a critical improper certificate validation flaw within GitLab Enterprise Edition's smartcard authentication implementation. This security weakness affects multiple version ranges including 11.6 through 16.4.3, 16.5 through 16.5.3, and 16.6 through 16.6.1, creating a significant attack surface for malicious actors targeting authenticated user sessions. The vulnerability specifically targets the certificate validation process used in smartcard-based authentication systems, which are designed to provide strong authentication through cryptographic keys stored on physical smartcards rather than traditional password-based methods.
The technical flaw stems from inadequate validation of X.509 certificates used in the smartcard authentication workflow, allowing attackers to exploit weaknesses in the certificate chain verification process. When smartcard authentication is enabled as an experimental feature, the system fails to properly validate certificate attributes and trust relationships that should prevent unauthorized authentication attempts. This issue is particularly dangerous because it enables credential substitution attacks where an attacker can leverage a victim's public key to impersonate that user within the GitLab environment, effectively bypassing the intended security controls of smartcard-based authentication.
The operational impact of this vulnerability extends beyond simple authentication bypasses, potentially enabling attackers to gain unauthorized access to sensitive repositories, code modifications, and administrative functions within GitLab instances. Since smartcard authentication is an experimental feature requiring manual administrator activation, organizations may not have properly assessed the security implications of enabling this functionality, creating additional attack vectors. The vulnerability affects the fundamental trust model of the authentication system, potentially allowing attackers to escalate privileges or access restricted resources that should only be available to legitimate users with valid smartcards.
Organizations should immediately apply the relevant security patches to versions 16.4.4, 16.5.4, and 16.6.2 to remediate this vulnerability. Administrators should also conduct comprehensive reviews of smartcard authentication configurations and consider disabling this experimental feature until proper security assessments can be completed. The vulnerability aligns with CWE-295 which addresses improper certificate validation and relates to ATT&CK technique T1078.004 for valid accounts using smartcards. Security teams should implement monitoring for unusual authentication patterns and certificate validation failures to detect potential exploitation attempts. Additionally, organizations should consider implementing multi-factor authentication controls and regular security audits of experimental features to prevent similar vulnerabilities from emerging in other authentication systems.