CVE-2024-11791

Executive Summary

CVE-2024-11791 is a critical stack-based buffer overflow vulnerability in Fuji Electric Monitouch V-SFT, specifically within the parsing of V8C files. The flaw allows remote code execution (RCE) when a user opens a malicious V8C file or visits a crafted web page. With a CVSS score of 7.8, the vulnerability requires user interaction but no authentication, making it a high-severity threat for industrial control system (ICS) environments. No public exploit code or patch is currently available, but the risk is elevated due to the potential for weaponization in targeted attacks against manufacturing and critical infrastructure.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby ecosystems. It affects a proprietary industrial software package (Fuji Electric Monitouch V-SFT) used for HMI/SCADA configuration. Supply chain risk is limited to direct software distribution channels.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Base Score: 7.8 (High)
• Attack Vector: Local (requires user to open a 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 can lead to full system compromise within the context of the current user, potentially allowing lateral movement in ICS networks.

Deep Dive & Mechanics

The vulnerability resides in the V8C file parser of Fuji Electric Monitouch V-SFT (version V8C). When parsing a specially crafted V8C file, the software 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), allowing an attacker to overwrite the return address and control program execution.

Root Cause: Lack of bounds checking on a strcpy or memcpy operation during V8C file parsing. The stack buffer is fixed-size, but the input data can exceed it, leading to corruption of adjacent stack memory.

Attack Vector: The attacker must convince a user to open a malicious V8C file (e.g., via email, download, or USB). Once opened, the overflow triggers arbitrary code execution with the privileges of the V-SFT process.

Impact: Full compromise of the workstation running V-SFT, which may be used to configure HMIs and PLCs. This could enable further attacks on industrial control systems.

Vulnerable vs. Patched Code

No official patch is available. The vulnerable code likely resembles:

void ParseV8CFile(char *fileData) {
    char buffer[256];
    // Vulnerable: no length check
    strcpy(buffer, fileData);
    // ... further processing
}

A patched version would include bounds checking:

void ParseV8CFile(char *fileData, size_t dataLen) {
    char buffer[256];
    if (dataLen >= sizeof(buffer)) {
        // Handle error
        return;
    }
    strncpy(buffer, fileData, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
    // ... further processing
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Fuji Electric Monitouch V-SFT V8C installed on a Windows target.
• Ability to deliver a malicious V8C file to the target.

Exploitation Steps:

1. Craft a malicious V8C file with a payload that overwrites the return address.
2. Use a ROP chain to bypass DEP/ASLR if needed.
3. Deliver the file via phishing or physical media.
4. When the user opens the file, the payload executes.

Example Payload Structure (Conceptual):

[V8C Header] + [Padding to buffer size] + [Overwritten return address] + [Shellcode]

Note: No public exploit code is available. This is a theoretical approach.

Blue Team

Detection:

• Monitor for unusual V8C file creation or modification.
• Use file integrity monitoring on V-SFT installation directories.
• Deploy endpoint detection rules for stack-based overflow patterns.

Hunting:

• Search for processes (V-SFT.exe) crashing with access violations.
• Look for suspicious child processes spawned by V-SFT.

Mitigation:

• Restrict execution of V-SFT to least privilege accounts.
• Use application whitelisting to block unknown V8C files.
• Isolate V-SFT workstations from the internet and untrusted networks.

Indicators of Compromise (IOCs)

• File Hashes: (No known samples; placeholder)
  • SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network: Outbound connections from V-SFT process to unknown IPs.
• Process: V-SFT.exe crashing with exception code 0xC0000005 (access violation).
• Registry: Unusual entries under HKLM\Software\Fuji Electric\Monitouch V-SFT.
• File System: Modified or new V8C files in unexpected locations.

Detection Engineering

YARA Rule

rule CVE_2024_11791_V8C_Overflow {
    meta:
        description = "Detects malicious V8C files exploiting CVE-2024-11791"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-11791"
    strings:
        $v8c_header = "V8C" ascii wide nocase
        $overflow_pattern = { 41 41 41 41 41 41 41 41 } // Example padding
    condition:
        $v8c_header and #overflow_pattern > 10
}

Sigma Rule

title: CVE-2024-11791 Fuji Electric V-SFT Stack Overflow
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2024-11791 via process crash or suspicious file access
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\V-SFT.exe'
        CommandLine|contains: '.v8c'
    condition: selection
falsepositives:
    - Legitimate V8C file usage
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11791 Fuji Electric V-SFT V8C File Download"; flow:to_server,established; content:"V8C"; nocase; fileext:"v8c"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable or restrict the use of Fuji Electric Monitouch V-SFT until a patch is available.
2. Implement strict file execution policies (e.g., AppLocker) to block untrusted V8C files.
3. Educate users not to open V8C files from untrusted sources.

Long-Term:

• Monitor vendor advisories for a security update.
• Consider network segmentation for ICS workstations.
• Deploy endpoint detection and response (EDR) with behavioral analysis.

Workaround: If V-SFT is essential, run it in a sandboxed environment or with reduced privileges.

Valters IT
Cyber Threat Intelligence & DevSecOps