CVE-2015-7362 in FortiClient Linux SSLVPN
Summary
by MITRE
Fortinet FortiClient Linux SSLVPN before build 2313, when installed on Linux in a home directory that is world readable and executable, allows local users to gain privileges via the helper/subroc setuid program.
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Analysis
by VulDB Data Team • 06/06/2018
The vulnerability identified as CVE-2015-7362 affects Fortinet FortiClient Linux SSLVPN versions prior to build 2313, presenting a critical privilege escalation risk when the software is installed in a world-readable and executable home directory. This flaw exploits the insecure handling of setuid programs within the FortiClient installation structure, specifically targeting the helper/subroc component that operates with elevated privileges. The vulnerability stems from inadequate permission controls on the installation directory and its contained executables, creating an avenue for local attackers to leverage existing user privileges and escalate to root access.
The technical implementation of this vulnerability involves the exploitation of weak file system permissions combined with the presence of setuid binaries in a compromised directory structure. When FortiClient is installed in a home directory that permits world read and execute permissions, the helper/subroc program can be manipulated by local users to execute arbitrary code with elevated privileges. This represents a classic privilege escalation vector where the attacker leverages the legitimate setuid functionality to gain unauthorized system-level access. The flaw operates under the principle of insecure file permissions, which falls under CWE-732, and specifically demonstrates improper privilege management in the context of setuid programs.
The operational impact of this vulnerability is significant for organizations deploying FortiClient Linux SSLVPN solutions, particularly in environments where user accounts might have overly permissive directory permissions. Attackers can exploit this weakness to establish persistent access to systems, potentially leading to complete system compromise and data exfiltration. The vulnerability is particularly dangerous in multi-user environments or shared systems where the default installation practices might inadvertently create accessible world-readable directories. This flaw can be exploited by any local user with access to the affected system, making it a severe concern for system administrators who must ensure proper file system permissions are maintained throughout the installation process.
Mitigation strategies for CVE-2015-7362 require immediate attention to directory permissions and software updates. Organizations should first ensure that FortiClient installations are performed in directories with restrictive permissions, eliminating world-read and world-execute access for the installation path. The recommended approach includes setting proper ownership and permissions on the installation directory, typically using chmod 755 or more restrictive settings as appropriate. Additionally, Fortinet released patches and updates addressing this vulnerability in build 2313 and subsequent versions, making software updates the primary remediation measure. Security teams should also implement monitoring for unauthorized changes to FortiClient installation directories and establish baseline configurations that prevent the creation of insecure permission structures during software deployment. This vulnerability aligns with ATT&CK technique T1068, which covers privilege escalation through local exploits, and emphasizes the importance of proper privilege management and secure configuration practices in maintaining system integrity.