CVE-2021-36183 in FortiClient
Summary
by MITRE • 11/02/2021
An improper authorization vulnerability [CWE-285] in FortiClient for Windows versions 7.0.1 and below and 6.4.2 and below may allow a local unprivileged attacker to escalate their privileges to SYSTEM via the named pipe responsible for Forticlient updates.
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Analysis
by VulDB Data Team • 05/05/2026
This vulnerability represents a critical authorization flaw in FortiClient for Windows systems that directly enables local privilege escalation from unprivileged user accounts to SYSTEM level access. The issue stems from improper access control mechanisms within the FortiClient update process, specifically through a named pipe that lacks adequate security restrictions. The vulnerability affects multiple versions including FortiClient 7.0.1 and earlier releases, as well as version 6.4.2 and below, indicating a widespread impact across the product lineage. Named pipes serve as inter-process communication mechanisms that typically require proper authentication and authorization checks to prevent unauthorized access. In this case, the named pipe responsible for FortiClient updates has been configured without appropriate security descriptors or access control lists that would normally restrict access to only authorized processes or users with elevated privileges.
The technical exploitation of this vulnerability allows a local attacker to leverage the improperly secured named pipe to execute malicious code with SYSTEM privileges. This represents a classic privilege escalation vector where an attacker with minimal user-level access can manipulate the update mechanism to gain complete system control. The attack scenario involves the local unprivileged user creating a malicious named pipe or exploiting the existing pipe to inject code that gets executed with elevated privileges by the FortiClient update service. This flaw directly maps to CWE-285 which specifically addresses improper authorization conditions in software systems, where access controls fail to properly verify that an operation is authorized. The vulnerability demonstrates a failure in the principle of least privilege and proper access control implementation within the FortiClient security architecture.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with complete system compromise capabilities. Once elevated to SYSTEM level, the attacker gains unrestricted access to all system resources, including the ability to modify or delete critical files, access encrypted data, install additional malware, and potentially establish persistent backdoors. This vulnerability is particularly concerning because it requires no network connectivity or remote exploitation capabilities, making it highly accessible to local attackers who may already have a foothold on the system through other means. The attack vector is relatively simple and reliable since the named pipe mechanism is typically designed to be accessible to legitimate update processes, but the security implementation fails to properly validate access rights. The vulnerability effectively undermines the security model of the FortiClient application and potentially compromises the entire endpoint security posture of organizations relying on this solution.
Organizations should immediately implement mitigations including updating to FortiClient versions that address this vulnerability, typically versions 7.0.2 or 6.4.3 and later. Security administrators should also consider implementing additional controls such as monitoring for unusual named pipe access patterns and restricting unnecessary local user privileges. The vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation through improper access control mechanisms. Network segmentation and least privilege principles should be enforced to minimize potential damage from such vulnerabilities. Additionally, organizations should conduct comprehensive vulnerability assessments to identify other potential authorization flaws in their endpoint security solutions and ensure proper patch management procedures are in place. The remediation process should include verification that the named pipe security descriptors have been properly configured with appropriate access control lists that restrict access to only authorized system processes.