CVE-2024-55414: Motorola Modem Driver Escalation Flaw

CVE-2024-55414 Overview

A critical vulnerability exists in the SmSerl64.sys driver, part of the Motorola SM56 Modem WDM Driver v6.12.23.0. This driver vulnerability allows low-privileged users to map physical memory through specially crafted IOCTL requests. The flaw enables privilege escalation, arbitrary code execution under high privileges, and information disclosure. Additionally, because the driver is legitimately signed, it can be exploited to bypass Microsoft's driver-signing policy, enabling attackers to deploy malicious code.

Critical Impact

This vulnerability allows low-privileged attackers to achieve kernel-level code execution by exploiting physical memory mapping capabilities in a signed Windows driver, potentially leading to complete system compromise.

Affected Products

• Motorola SM56 Modem WDM Driver SmSerl64.sys v6.12.23.0
• Windows systems with the vulnerable driver installed
• Systems where the signed driver could be loaded for BYOVD (Bring Your Own Vulnerable Driver) attacks

Discovery Timeline

• 2025-01-07 - CVE-2024-55414 published to NVD
• 2025-01-08 - Last updated in NVD database

Technical Details for CVE-2024-55414

Vulnerability Analysis

This driver vulnerability (CWE-77: Improper Neutralization of Special Elements used in a Command) resides in the SmSerl64.sys kernel-mode driver. The vulnerability stems from improper validation of IOCTL (Input/Output Control) requests, allowing user-mode applications to directly map physical memory into their address space.

When a low-privileged user sends a specially crafted IOCTL request to the vulnerable driver, it fails to properly validate the request parameters. This allows the attacker to specify arbitrary physical memory regions to be mapped into user-accessible virtual memory. Once physical memory is mapped, an attacker can read and write to kernel memory structures, effectively gaining kernel-level privileges.

The signed nature of this driver makes it particularly dangerous in BYOVD (Bring Your Own Vulnerable Driver) attack scenarios, where threat actors intentionally deploy known-vulnerable but legitimately signed drivers to bypass Windows security controls.

Root Cause

The root cause lies in the improper handling of IOCTL requests within the SmSerl64.sys driver. The driver exposes functionality that allows physical memory mapping without adequate privilege checks or input validation. Specifically, the driver fails to:

1. Verify that the calling process has sufficient privileges to perform physical memory operations
2. Validate the physical memory address ranges requested in IOCTL calls
3. Restrict access to sensitive kernel memory regions

This design flaw allows any user with the ability to open a handle to the driver to request arbitrary physical memory mappings.

Attack Vector

The attack vector involves a local attacker with low-level privileges who can interact with the vulnerable driver through standard Windows device I/O mechanisms:

1. Driver Access: The attacker opens a handle to the SmSerl64.sys driver device
2. IOCTL Request Construction: A specially crafted IOCTL request is constructed specifying target physical memory addresses
3. Memory Mapping: The driver processes the request and maps the specified physical memory into the attacker's process space
4. Privilege Escalation: With direct access to kernel memory, the attacker can modify process tokens or inject code into kernel space to achieve SYSTEM-level privileges

In BYOVD scenarios, attackers may deliberately install this vulnerable driver on target systems specifically to exploit this capability, even if the driver was not previously present.

Detection Methods for CVE-2024-55414

Indicators of Compromise

• Presence of SmSerl64.sys driver file (version 6.12.23.0) on systems where Motorola modem hardware is not expected
• Unexpected loading of the SmSerl64.sys driver, particularly on systems without Motorola SM56 modem hardware
• IOCTL activity targeting the SmSerl64 driver device from non-modem related processes
• Token manipulation or privilege escalation events following driver interaction

Detection Strategies

• Monitor for driver load events involving SmSerl64.sys using Windows Event Logs or EDR solutions
• Implement driver blocklisting policies to prevent loading of known-vulnerable driver versions
• Use Windows Defender Application Control (WDAC) or similar tools to block unsigned or known-vulnerable drivers
• Monitor DeviceIoControl API calls targeting suspicious device handles from unexpected processes

Monitoring Recommendations

• Enable driver load auditing in Windows Security event logs (Event ID 7045 for service installation)
• Deploy endpoint detection rules for BYOVD attack patterns
• Monitor for process privilege changes following interaction with legacy driver devices
• Implement SentinelOne Singularity platform for real-time kernel-level monitoring and driver interaction analysis

How to Mitigate CVE-2024-55414

Immediate Actions Required

• Remove or disable the vulnerable SmSerl64.sys driver (v6.12.23.0) from all affected systems
• Add the vulnerable driver hash to blocklist policies to prevent installation
• Review systems for unauthorized driver installations that may indicate BYOVD attack attempts
• Enable Hypervisor-Enforced Code Integrity (HVCI) to provide additional protection against kernel exploitation

Patch Information

No vendor patch information is currently available for this vulnerability. Organizations should check the Motorola website for any security updates. As the Motorola SM56 Modem is legacy hardware, a patch may not be forthcoming, and removal of the driver is recommended.

For additional technical details, refer to the GitHub CVE-2024-55414 README.

Workarounds

• Uninstall the Motorola SM56 Modem WDM Driver if the hardware is not in active use
• Implement Windows Defender Application Control (WDAC) policies to block the vulnerable driver
• Enable Microsoft Vulnerable Driver Blocklist feature on Windows 11 and Windows 10 systems
• Use application control solutions to prevent unauthorized driver loading

# Block vulnerable driver using Windows Defender Application Control
# Add the following to your WDAC policy to deny the vulnerable driver

# First, get the driver hash
Get-FileHash -Path "C:\Windows\System32\drivers\SmSerl64.sys" -Algorithm SHA256

# Create or update WDAC deny rule for the driver
# Add to your existing WDAC policy XML:
# <Deny ID="ID_DENY_SMSERL64" FriendlyName="SmSerl64.sys vulnerable driver" 
#   Hash="[SHA256_HASH_VALUE]" />