CVE-2024-11790

Executive Summary

CVE-2024-11790 is a critical stack-based buffer overflow vulnerability in Fuji Electric Monitouch V-SFT, specifically within the parsing of V10 files. This vulnerability allows remote attackers to execute arbitrary code on affected installations, but requires user interaction (e.g., opening a malicious file or visiting a malicious page). The flaw stems from improper validation of user-supplied data length before copying it to a stack-based buffer. With a CVSS score of 7.8, 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 has been reported via ZDI-CAN-24449.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Attack Vector: Local (AV:L) – Exploitation requires user interaction.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: Required (UI:R) – Victim must open a malicious file or page.
• Scope: Unchanged (S:U) – Vulnerability affects only the vulnerable component.
• Confidentiality Impact: High (C:H) – Full data access possible.
• Integrity Impact: High (I:H) – Arbitrary code execution.
• Availability Impact: High (A:H) – Potential system crash or compromise.

Threat Level: High. Exploitation could lead to full compromise of the HMI configuration workstation, potentially allowing attackers to manipulate industrial processes or pivot to other ICS assets.

Deep Dive & Mechanics

The vulnerability exists in the V10 file parsing module of Fuji Electric Monitouch V-SFT. When the software processes a specially crafted V10 file, it fails to validate the length of user-supplied data before copying it to a fixed-size stack buffer. This results in a classic stack-based buffer overflow (CWE-121). An attacker can overwrite the return address and other critical stack data, leading to arbitrary code execution in the context of the current process (typically the user running the V-SFT application).

The attack vector is local, requiring the victim to open a malicious V10 file (e.g., via email, download, or USB). Once executed, the attacker gains the same privileges as the logged-in user, which could be an administrator in many ICS environments.

Vulnerable vs. Patched Code

Since no patch details are available, a generic comparison is provided:

Vulnerable Code (Conceptual):

void parse_v10_file(char *data) {
    char buffer[256];
    // No length check
    strcpy(buffer, data);  // Stack overflow if data > 255 bytes
}

Patched Code (Conceptual):

void parse_v10_file(char *data) {
    char buffer[256];
    // Proper length validation
    if (strlen(data) >= sizeof(buffer)) {
        // Handle error
        return;
    }
    strcpy(buffer, data);
}

The fix would involve adding bounds checking before copying data to the stack buffer, or using safer functions like strncpy with proper null-termination.

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Setup:

• Target: Windows 10/11 with Fuji Electric Monitouch V-SFT (vulnerable version).
• Attacker: Kali Linux with Metasploit or custom exploit.
• Tools: Python, Immunity Debugger, Mona.py, msfvenom.

Exploitation Steps:

1. Craft Malicious V10 File: Use a Python script to create a V10 file with a payload that triggers the buffer overflow.
2. Deliver File: Send the file via email or host it on a malicious website.
3. Trigger Vulnerability: Victim opens the file in V-SFT.
4. Gain Code Execution: The overflow overwrites the return address, redirecting execution to shellcode.

Example Payload Generation (msfvenom):

msfvenom -p windows/exec CMD=calc.exe -f python -b "\x00" > payload.py

Python Exploit Skeleton:

import struct

# Shellcode (calc.exe for demo)
shellcode = b"\x90" * 100  # Replace with actual shellcode

# Buffer overflow offset (to be determined via fuzzing)
offset = 260
eip = struct.pack("<I", 0x12345678)  # Address of JMP ESP

# Craft malicious V10 file
payload = b"A" * offset + eip + shellcode
with open("malicious.v10", "wb") as f:
    f.write(payload)

Blue Team (Defense)

Detection & Prevention:

• User Awareness: Train users not to open untrusted V10 files.
• Application Whitelisting: Restrict execution of V-SFT to authorized users only.
• Memory Protection: Enable ASLR, DEP, and CFG on Windows.
• Network Segmentation: Isolate HMI workstations from the internet.
• File Integrity Monitoring: Monitor for creation of .v10 files in suspicious locations.

Hunting:

• Monitor for crashes of V-SFT.exe or related processes.
• Look for unusual child processes spawned by V-SFT (e.g., cmd.exe, powershell.exe).
• Analyze network connections from V-SFT workstations for anomalous outbound traffic.

Indicators of Compromise (IOCs)

• File Hashes: (Example – replace with actual when available)
  • malicious.v10 – SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Process Anomalies:
  • V-SFT.exe spawning cmd.exe or powershell.exe.
  • Unexpected memory access violations in V-SFT.exe.
• Network Indicators:
  • Outbound connections from V-SFT workstation to unknown IPs (e.g., on port 80/443).
• Registry Changes:
  • Unusual entries under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run.

Detection Engineering

YARA Rule

rule CVE_2024_11790_Malicious_V10 {
    meta:
        description = "Detects malicious V10 files exploiting CVE-2024-11790"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-11790"
    strings:
        $magic = "V10"  // File header or magic bytes
        $overflow_pattern = /AAAA[A-Z]{250,}/  // Long string pattern
    condition:
        $magic at 0 and #overflow_pattern > 0
}

Sigma Rule

title: Suspicious V-SFT Process Behavior
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2024-11790 via abnormal child processes
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: 'V-SFT.exe'
        Image|endswith:
            - 'cmd.exe'
            - 'powershell.exe'
            - 'wscript.exe'
            - 'cscript.exe'
    condition: selection
falsepositives:
    - Legitimate administrative tasks
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11790 - Potential V10 File Download"; flow:to_server,established; content:"|56 31 30|"; depth:3; content:"|41 41 41 41|"; distance:0; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

• Patch: Await official patch from Fuji Electric. Contact vendor for updates.
• Workaround: Disable V10 file parsing if not needed, or use a sandbox to open untrusted files.
• Mitigation:
  • Implement strict file upload/download policies.
  • Use endpoint detection and response (EDR) to monitor for exploitation attempts.
  • Apply principle of least privilege to user accounts.
  • Enable Windows Defender Exploit Guard (e.g., Control Flow Guard, Data Execution Prevention).

Valters IT – Securing Industrial Environments