CVE-2024-11789

Executive Summary

CVE-2024-11789 is a stack-based buffer overflow vulnerability in Fuji Electric Monitouch V-SFT, specifically during the parsing of V10 files. The flaw allows remote code execution (RCE) in the context of the current process, requiring user interaction (e.g., opening a malicious file or visiting a malicious page). With a CVSS score of 7.8 (High), this vulnerability poses a significant risk to industrial control systems (ICS) environments where Monitouch V-SFT is used for HMI (Human-Machine Interface) configuration. No public exploit or patch details are currently available, but the vulnerability is confirmed by ZDI (ZDI-CAN-24448).

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector: Local (requires user to open a malicious file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: High. Exploitation could lead to full compromise of the workstation running V-SFT, potentially allowing lateral movement within an OT network.

Deep Dive & Mechanics

The vulnerability resides in the V10 file parsing module of Fuji Electric Monitouch V-SFT. When the application processes a specially crafted V10 file, it fails to validate the length of user-supplied data before copying it to a stack-based buffer. This results in a classic stack buffer overflow (CWE-121). An attacker can overwrite the return address or other critical stack data to hijack execution flow and achieve arbitrary code execution.

Key Technical Details:

• Root Cause: Lack of bounds checking on data copied to a stack buffer during V10 file parsing.
• Exploitation Vector: Malicious V10 file delivered via phishing, drive-by download, or USB drop.
• Impact: Full control of the affected process, enabling code execution with the privileges of the logged-in user.
• No ASLR/DEP bypass required if the attacker can reliably overwrite the return address with a known address (e.g., in older Windows versions or with specific compiler settings).

Vulnerable vs. Patched Code

Since no patch or source code is publicly available, a generic comparison is provided:

Vulnerable Code Pattern (C-like pseudocode):

void ParseV10File(char *fileData) {
    char buffer[256];
    // No length check
    strcpy(buffer, fileData); // Stack overflow if fileData > 255 bytes
}

Patched Code Pattern:

void ParseV10File(char *fileData, size_t dataLen) {
    char buffer[256];
    if (dataLen >= sizeof(buffer)) {
        // Handle error
        return;
    }
    memcpy(buffer, fileData, dataLen); // Safe copy
}

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Environment:

• Windows 10/11 VM with Fuji Electric Monitouch V-SFT installed (vulnerable version).
• Attacker machine with Python3 and Metasploit (or custom exploit).

Exploit Steps:

1. Craft a malicious V10 file with a payload that overwrites the return address.
2. Use a stack-based buffer overflow technique (e.g., jmp esp gadget for Windows).
3. Deliver the file to the victim (e.g., via email or web download).
4. When the victim opens the file in V-SFT, the exploit triggers and executes shellcode.

Example Python Exploit Skeleton:

import struct

# Shellcode (e.g., calc.exe or reverse shell)
shellcode = b"\x90" * 100  # NOP sled
shellcode += b"\xcc" * 4    # INT3 for testing

# Buffer overflow
buffer = b"A" * 260         # Fill buffer
buffer += struct.pack("<I", 0x7C86467B)  # jmp esp address (example)
buffer += shellcode

with open("malicious.v10", "wb") as f:
    f.write(buffer)

Note: No public exploit code is available; this is a conceptual example.

Blue Team (Detection & Defense)

Detection:

• Monitor for abnormal V10 file sizes or unusual file access patterns.
• Use endpoint detection and response (EDR) to detect stack-based overflow behavior (e.g., SEH overwrite, return address corruption).
• Enable ASLR and DEP on all systems.

Defense:

• Restrict execution of V-SFT to least privilege accounts.
• Use application whitelisting to block untrusted V10 files.
• Deploy network segmentation to limit lateral movement from compromised workstations.

Indicators of Compromise (IOCs)

• File Hashes: (No known samples yet)
• Network Indicators: Outbound connections from V-SFT process to attacker IPs (if reverse shell used).
• Process Anomalies: V-SFT crashing or spawning child processes (e.g., cmd.exe, powershell.exe).
• Registry/File System: Unusual files in %TEMP% or startup folders.

Detection Engineering

YARA Rule

rule CVE_2024_11789_V10_Overflow {
    meta:
        description = "Detects malicious V10 files exploiting CVE-2024-11789"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $overflow_pattern = { 41 41 41 41 41 41 41 41 } // 'AAAAAAAA' pattern
        $v10_header = "V10" ascii
    condition:
        $v10_header at 0 and #overflow_pattern > 10
}

Sigma Rule

title: Suspicious V10 File Access Leading to Stack Overflow
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to open malicious V10 files that may trigger CVE-2024-11789
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\V-SFT.exe'
        CommandLine|contains: '.v10'
    condition: selection
falsepositives:
    - Legitimate V10 file editing
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11789 V10 File Download"; flow:to_server,established; content:"V10"; offset:0; depth:3; content:"|41 41 41 41|"; distance:0; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

• Patch: No official patch available. Contact Fuji Electric for updates.
• Mitigation:
  • Disable or restrict V10 file parsing if not required.
  • Implement strict file validation (e.g., only allow V10 files from trusted sources).
  • Use sandboxing or virtualization for V-SFT execution.
  • Apply Windows mitigations (ASLR, DEP, CFG).
• Workaround: Convert V10 files to a safer format or use alternative HMI configuration tools.

Valters IT
Securing Industrial Environments, One CVE at a Time.