CVE-2015-5735 in FortiClient
Summary
by MITRE
The (1) mdare64_48.sys, (2) mdare32_48.sys, (3) mdare32_52.sys, and (4) mdare64_52.sys drivers in Fortinet FortiClient before 5.2.4 allows local users to write to arbitrary memory locations via a 0x226108 ioctl call.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 06/14/2022
The vulnerability identified as CVE-2015-5735 affects the Fortinet FortiClient security software across multiple driver components including mdare64_48.sys, mdare32_48.sys, mdare32_52.sys, and mdare64_52.sys. This represents a critical privilege escalation flaw that exists within the kernel-mode driver architecture of the FortiClient endpoint protection solution. The affected drivers are part of Fortinet's antivirus and security framework designed to protect endpoints from various malware threats. The vulnerability stems from improper input validation within the ioctl handling mechanism, specifically when processing the 0x226108 command code. This flaw allows local attackers who already have user-level access to the system to escalate their privileges and gain arbitrary write access to kernel memory regions.
The technical implementation of this vulnerability involves a classic buffer overflow or memory corruption issue within the driver's ioctl dispatch routine. When the 0x226108 ioctl command is invoked, the driver fails to properly validate the input parameters or the size of the data structure being passed. This lack of proper bounds checking enables an attacker to manipulate the driver's memory operations, potentially allowing them to write data to any memory location within the kernel space. The impact is particularly severe because it bypasses normal kernel protection mechanisms and allows direct memory manipulation that could be used to modify critical system structures, inject malicious code, or disable security features. This type of vulnerability is classified under CWE-121 as a stack-based buffer overflow or more specifically as a memory corruption vulnerability in kernel drivers.
From an operational perspective, this vulnerability creates a significant risk for organizations using FortiClient versions prior to 5.2.4, as it provides a pathway for local attackers to escalate privileges from standard user accounts to system-level access. The attack vector is particularly concerning because it requires only local system access, meaning that an attacker who has already compromised a user account or gained physical access to a device can leverage this flaw to gain complete control over the system. The implications extend beyond simple privilege escalation, as the arbitrary write capability could be used to modify system call tables, disable security modules, or install rootkits that persist across reboots. This vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation and represents a common attack pattern where initial access is leveraged to achieve higher system privileges.
The mitigation strategy for CVE-2015-5735 involves immediate deployment of Fortinet FortiClient version 5.2.4 or later, which includes patches that address the ioctl parameter validation issues. Organizations should also implement monitoring for suspicious ioctl activity patterns and consider disabling unnecessary driver functionalities when possible. System administrators should conduct thorough security assessments of their endpoint protection configurations and ensure that all security software is kept up to date with the latest patches. Additionally, implementing principle of least privilege access controls and regular security audits can help reduce the risk exposure from such vulnerabilities. The patch addresses the root cause by adding proper input validation and bounds checking to the ioctl handling code, ensuring that memory operations are restricted to legitimate kernel memory regions and preventing arbitrary write access to system memory.