CVE-2015-5737 in FortiClient
Summary
by MITRE
The (1) mdare64_48.sys, (2) mdare32_48.sys, (3) mdare32_52.sys, (4) mdare64_52.sys, and (5) Fortishield.sys drivers in Fortinet FortiClient before 5.2.4 do not properly restrict access to the API for management of processes and the Windows registry, which allows local users to obtain a privileged handle to a PID and possibly have unspecified other impact, as demonstrated by a 0x2220c8 ioctl call.
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Analysis
by VulDB Data Team • 06/14/2022
The vulnerability identified as CVE-2015-5737 affects multiple kernel-mode drivers within Fortinet FortiClient versions prior to 5.2.4, specifically targeting the mdare64_48.sys, mdare32_48.sys, mdare32_52.sys, mdare64_52.sys, and Fortishield.sys components. This issue represents a critical access control flaw that undermines the security boundaries between user-mode applications and kernel-mode drivers, creating potential privilege escalation pathways for local attackers. The vulnerability stems from improper access restrictions within the driver's application programming interface, which governs management operations for processes and registry access. The affected drivers are part of FortiClient's endpoint protection suite and are responsible for various security functions including process monitoring and system registry management.
The technical implementation of this vulnerability involves a specific ioctl (input/output control) call with the code 0x2220c8 that allows local users to obtain privileged handles to process identifiers. This flaw falls under CWE-284, which describes improper access control vulnerabilities where insufficient restrictions are placed on access to system resources. The vulnerability operates at the kernel level, where the drivers fail to properly validate or authenticate API calls that would normally be restricted to privileged system processes. This allows unprivileged local users to manipulate process handles and registry entries through these exposed driver interfaces, effectively bypassing normal Windows security controls. The improper access control manifests when the driver API does not adequately verify the calling process's privileges before executing sensitive operations.
The operational impact of this vulnerability extends beyond simple privilege escalation, as local attackers could potentially manipulate system processes and registry entries to achieve persistent access or execute arbitrary code with kernel-level privileges. The vulnerability affects systems running Windows operating systems where FortiClient is installed, creating a significant risk for enterprise environments where local user access is not strictly controlled. Attackers could leverage this flaw to escalate privileges from standard user accounts to system-level access, potentially leading to complete system compromise. The registry manipulation capabilities could allow attackers to modify system configurations, disable security features, or establish persistence mechanisms within the compromised system. This vulnerability aligns with ATT&CK technique T1068, which covers 'Local Privilege Escalation' through kernel exploits, and T1112, which addresses 'Modify Registry' operations that can be used for persistence.
Mitigation strategies for CVE-2015-5737 primarily focus on updating FortiClient to version 5.2.4 or later, where Fortinet has implemented proper access controls and privilege validation within the affected drivers. Organizations should also implement strict access controls to limit local user privileges, particularly on systems running FortiClient, and conduct regular security assessments to identify potentially vulnerable installations. Network segmentation and monitoring for suspicious registry modifications or process manipulation activities can help detect exploitation attempts. System administrators should consider implementing additional security measures such as driver signature enforcement, application whitelisting, and monitoring for unusual ioctl calls to the affected driver interfaces. The vulnerability demonstrates the critical importance of proper kernel-mode driver security implementation and highlights the need for thorough security testing of system-level components that interface with sensitive operating system functions.