CVE-2019-6788 in Community Edition
Summary
by MITRE
An issue was discovered in GitLab Community and Enterprise Edition before 11.5.8, 11.6.x before 11.6.6, and 11.7.x before 11.7.1. It allows Information Disclosure (issue 3 of 6). For installations using GitHub or Bitbucket OAuth integrations, it is possible to use a covert redirect to obtain the user OAuth token for those services.
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Analysis
by VulDB Data Team • 12/18/2023
The vulnerability identified as CVE-2019-6788 represents a critical information disclosure flaw within GitLab's authentication infrastructure that affected multiple versions of the platform. This security issue specifically targeted installations utilizing third-party OAuth integrations with GitHub and Bitbucket services, creating a pathway for unauthorized access to sensitive authentication tokens. The vulnerability stems from inadequate validation of redirect URLs during the OAuth authentication process, allowing malicious actors to exploit this weakness for credential harvesting.
The technical implementation of this vulnerability resides in GitLab's OAuth redirect handling mechanism where the system failed to properly validate the target URLs specified during the authentication flow. When users attempted to authenticate through GitHub or Bitbucket integrations, the application would accept arbitrary redirect URIs without sufficient verification, enabling attackers to craft malicious redirect URLs that could capture the OAuth access tokens. This flaw operates at the application layer and directly violates security principles related to input validation and authentication flow integrity. The vulnerability aligns with CWE-601 Open Redirect vulnerability classification, which specifically addresses the risk of redirecting users to untrusted domains during authentication processes.
The operational impact of this vulnerability extends beyond simple information disclosure, as OAuth tokens represent highly sensitive credentials that can be immediately exploited for unauthorized access to connected services. Attackers could leverage this vulnerability to obtain valid OAuth tokens for affected users, potentially gaining access to their GitHub or Bitbucket repositories, organizations, and associated resources. The covert nature of the redirect mechanism makes detection particularly challenging, as the malicious activity would appear to originate from legitimate authentication flows. This vulnerability particularly affects organizations that rely heavily on third-party authentication services and could result in significant compromise of developer accounts and source code repositories.
Organizations using GitLab versions prior to the patched releases should immediately implement mitigation strategies including immediate upgrade to the patched versions 11.5.8, 11.6.6, or 11.7.1 respectively. Additional protective measures include reviewing and validating all OAuth integration configurations, implementing network-level restrictions on external redirect URLs, and monitoring authentication logs for suspicious redirect patterns. Security teams should also consider implementing additional authentication controls such as two-factor authentication for privileged accounts and regular token rotation for OAuth integrations. The vulnerability demonstrates the critical importance of proper input validation in authentication flows and aligns with ATT&CK technique T1566.002 for credential access through phishing with redirects, highlighting the need for comprehensive security controls around third-party authentication integrations.