CVE-2019-6786 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 has Incorrect Access Control (issue 1 of 3). The contents of an LFS object can be accessed by an unauthorized user, if the file size and OID are known.
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Analysis
by VulDB Data Team • 12/18/2023
The vulnerability described in CVE-2019-6786 represents a critical access control flaw within GitLab's Large File Storage (LFS) implementation across multiple versions of the platform. This issue affects both Community and Enterprise editions, with specific affected versions including releases prior to 11.5.8, 11.6.6, and 11.7.1. The flaw stems from inadequate authorization checks that allow malicious actors to bypass normal access controls and retrieve sensitive LFS object contents when they possess knowledge of the file size and Object Identifier (OID). The vulnerability manifests as a failure in the authentication and authorization mechanisms that should normally protect LFS assets from unauthorized access.
This access control weakness falls under CWE-284, which specifically addresses improper access control vulnerabilities where systems fail to properly enforce access restrictions. The technical implementation flaw occurs within GitLab's LFS module where the system relies on the OID and file size as sufficient identifiers for access decisions rather than properly validating user permissions. The vulnerability creates a scenario where an attacker with minimal information can construct direct access requests to LFS objects, essentially bypassing the normal GitLab user authentication and authorization flow that should govern access to repository assets. This represents a fundamental breakdown in the security model where object identifiers become the sole determinant of access rather than proper user context validation.
The operational impact of this vulnerability extends beyond simple unauthorized data access, as it can lead to significant data exposure and potential compromise of sensitive information stored within GitLab repositories. Attackers can leverage this weakness to retrieve confidential files, source code, binary assets, or other repository content that should only be accessible to authorized team members. The vulnerability is particularly concerning because it does not require elevated privileges or complex attack vectors - simply knowing the OID and file size of a target LFS object enables access. This makes the attack surface broad and accessible to anyone who can obtain this minimal information through reconnaissance or other means, potentially affecting organizations that store proprietary code, sensitive documentation, or intellectual property within their GitLab instances.
Organizations should implement immediate mitigations including upgrading to the patched versions mentioned in the advisory, which address the core access control implementation issues. System administrators should also consider implementing additional monitoring for LFS access patterns and conducting security reviews of repository permissions to identify any potential unauthorized access that may have occurred. The vulnerability highlights the importance of proper access control design principles and the necessity of implementing defense-in-depth strategies. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and credential access, where attackers can leverage weak access controls to gain unauthorized access to sensitive data. Organizations should also review their overall security posture and ensure proper segmentation of sensitive repositories, implement regular security assessments, and maintain up-to-date patch management procedures to prevent similar issues from arising in other components of their GitLab infrastructure.