CVE-2021-22127 in FortiClient
Summary
by MITRE • 04/06/2022
An improper input validation vulnerability in FortiClient for Linux 6.4.x before 6.4.3, FortiClient for Linux 6.2.x before 6.2.9 may allow an unauthenticated attacker to execute arbitrary code on the host operating system as root via tricking the user into connecting to a network with a malicious name.
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Analysis
by VulDB Data Team • 04/08/2022
This vulnerability represents a critical input validation flaw in FortiClient for Linux versions prior to 6.4.3 and 6.2.9, classified under CWE-20 Improper Input Validation. The vulnerability arises from insufficient validation of network names or identifiers during the connection process, specifically when users attempt to connect to networks with maliciously crafted names. Attackers can exploit this weakness by crafting specially formatted network names that, when processed by the vulnerable FortiClient software, trigger arbitrary code execution with root privileges.
The attack vector requires social engineering to trick users into connecting to a malicious network, making this a user-interaction dependent vulnerability. When a user attempts to connect to a network with a specially crafted name, the FortiClient software fails to properly validate the input, allowing malicious code embedded within the network name to be executed in the context of the root user. This represents a severe privilege escalation vulnerability that bypasses normal authentication mechanisms and directly compromises system integrity.
The operational impact of this vulnerability is substantial as it allows unauthenticated attackers to gain root-level access to affected systems without requiring any credentials or prior access. This compromises the entire host operating system, potentially enabling complete system takeover, data exfiltration, and persistence mechanisms. The vulnerability affects multiple versions of FortiClient for Linux, indicating a widespread exposure across various deployment scenarios including enterprise networks and individual workstations.
Mitigation strategies should focus on immediate patching of affected FortiClient versions to 6.4.3 or later and 6.2.9 or later releases. Organizations should also implement network segmentation to limit the attack surface and monitor for suspicious network connection attempts. Security controls should include user awareness training to recognize social engineering attempts and network monitoring to detect anomalous connection patterns. From an ATT&CK framework perspective, this vulnerability maps to T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, highlighting the need for comprehensive endpoint protection and privilege management controls. The vulnerability demonstrates the critical importance of input validation in network client applications and the potential for seemingly benign user interaction points to become critical attack vectors in enterprise security infrastructures.