CVE-2016-8497 in FortiOS
Summary
by MITRE
An escalation of privilege vulnerability in Fortinet FortiClient SSL_VPN Linux versions available with FortiOS 5.4.3 and below allows an attacker to gain root privilege via the subproc file.
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Analysis
by VulDB Data Team • 12/25/2020
The CVE-2016-8497 vulnerability represents a critical escalation of privilege flaw affecting Fortinet FortiClient SSL_VPN Linux implementations running on FortiOS 5.4.3 and earlier versions. This vulnerability specifically targets the subproc file component within the SSL_VPN client architecture, creating a pathway for unauthorized users to elevate their privileges from standard user level to root access. The flaw exists within the privilege management mechanisms of the FortiClient SSL_VPN client software, which is designed to provide secure remote access to corporate networks through SSL-based virtual private network connections.
The technical exploitation of this vulnerability occurs through manipulation of the subproc file handling within the FortiClient SSL_VPN Linux client. When the client processes certain subproc operations, it fails to properly validate or restrict file access permissions, allowing an attacker with local access to manipulate the subproc file in a manner that grants elevated privileges. This represents a classic privilege escalation vector where insufficient access control checks enable a malicious user to bypass normal security boundaries. The vulnerability is categorized under CWE-269, which specifically addresses improper privilege management, and aligns with ATT&CK technique T1068, which covers local privilege escalation through exploitation of system vulnerabilities.
The operational impact of this vulnerability is severe as it fundamentally undermines the security model of the FortiClient SSL_VPN implementation. Once exploited, attackers can gain complete root access to the compromised system, enabling them to install malware, modify system files, access all user data, and potentially use the compromised machine as a pivot point to attack other systems within the network. The vulnerability affects organizations that rely on FortiClient SSL_VPN for remote access, particularly those with less than 5.4.3 FortiOS versions, creating a significant risk for enterprises with remote workforce capabilities. This flaw can be exploited by any user with local access to a vulnerable system, making it particularly dangerous in environments where physical access controls are not stringent.
Organizations affected by this vulnerability should immediately implement mitigations including upgrading to FortiOS 5.4.4 or later versions where the issue has been resolved through proper subproc file access controls and privilege validation mechanisms. System administrators should also implement additional security measures such as restricting local user access to vulnerable systems, monitoring for suspicious subproc file operations, and conducting regular security assessments to identify potential exploitation attempts. The vulnerability demonstrates the importance of proper privilege separation in security software and highlights the need for comprehensive testing of privilege management components in remote access solutions. Fortinet has addressed this issue through firmware updates that strengthen the subproc file handling and implement proper access controls to prevent unauthorized privilege elevation.