CVE-2026-3848 in Community Edition
Summary
by MITRE • 03/11/2026
GitLab has remediated an issue in GitLab CE/EE affecting all versions from 8.11 before 18.7.6, 18.8 before 18.8.6, and 18.9 before 18.9.2 that could have allowed an authenticated user to make unintended internal requests through proxy environments under certain conditions due to improper input validation in import functionality.
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Analysis
by VulDB Data Team • 03/14/2026
This vulnerability exists within GitLab's import functionality where authenticated users can manipulate proxy configurations to make unintended internal requests. The flaw stems from inadequate input validation mechanisms that fail to properly sanitize proxy settings during the import process. When users configure import operations through proxy environments, the system does not adequately verify the legitimacy of proxy addresses or parameters, creating a potential attack vector for privilege escalation and internal network reconnaissance.
The technical implementation of this vulnerability allows an authenticated user to craft malicious proxy configurations that bypass normal access controls. This occurs specifically when GitLab processes import operations through proxy servers, where the application fails to validate that proxy addresses conform to expected patterns or restrictions. The vulnerability is particularly concerning because it operates within the context of authenticated sessions, meaning attackers need only valid user credentials to exploit this weakness. This aligns with CWE-20, which addresses improper input validation as a fundamental security flaw that enables various attack vectors including command injection and information disclosure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable attackers to perform unauthorized internal network scanning or even execute commands on internal systems. An attacker could potentially configure a proxy that routes requests to internal services, allowing them to probe network topology, access internal APIs, or exfiltrate sensitive data from behind firewalls. This represents a significant risk in environments where GitLab serves as an integration point for various internal services, as it could provide a foothold for lateral movement attacks. The vulnerability affects a broad range of GitLab versions, making it particularly dangerous as organizations may have extended deployment periods without immediate patching.
Organizations should immediately implement the vendor-provided patches for GitLab versions 18.7.6, 18.8.6, and 18.9.2 to address this vulnerability. Network segmentation and proxy configuration reviews should be conducted to ensure that import operations are properly restricted and monitored. Implementing strict proxy validation rules and monitoring for unusual proxy configurations during import operations can help detect potential exploitation attempts. Additionally, organizations should consider implementing privilege separation for import operations and limiting the scope of proxy configurations available to authenticated users. This vulnerability demonstrates the importance of input validation in web applications and aligns with ATT&CK technique T1071.004, which covers application layer protocol tunneling, as the malicious proxy configurations essentially create unauthorized tunnels through the application's network interfaces.