CVE-2024-11794

Executive Summary

CVE-2024-11794 is a critical out-of-bounds write vulnerability in Fuji Electric Monitouch V-SFT, specifically during the parsing of V10 files. This flaw allows remote attackers to execute arbitrary code on affected installations, but requires user interaction (e.g., visiting a malicious page or opening a malicious file). The vulnerability stems from improper validation of user-supplied data, leading to a write past the end of an allocated buffer. With a CVSS score of 7.8, it 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 was reported via ZDI-CAN-24504.

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 (AV): Local (requires user interaction)
• Attack Complexity (AC): Low
• Privileges Required (PR): None
• User Interaction (UI): Required (victim must open a malicious file)
• Scope (S): Unchanged
• Confidentiality (C): High
• Integrity (I): High
• Availability (A): High

Threat Level: High. Exploitation can lead to full system compromise within the context of the current process, potentially allowing attackers to pivot to other ICS components.

Deep Dive & Mechanics

The vulnerability resides in the parsing logic of V10 files within Fuji Electric Monitouch V-SFT. When the application processes a specially crafted V10 file, it fails to validate the size of user-supplied data before writing it to a fixed-size buffer. This results in an out-of-bounds write, overwriting adjacent memory regions. An attacker can craft a malicious V10 file that, when opened by a user, triggers this buffer overflow, leading to arbitrary code execution.

The specific flaw is a classic stack-based or heap-based buffer overflow (CWE-787). The lack of proper bounds checking allows the attacker to control the overflow data, which can be used to overwrite return addresses, function pointers, or other critical data structures. Since the vulnerability is triggered during file parsing, it is particularly dangerous in environments where users routinely open V10 files from untrusted sources (e.g., email attachments, downloads).

Vulnerable vs. Patched Code

No patched version or code diff is available. The vulnerable code likely resembles:

void parse_v10_file(char *data, size_t size) {
    char buffer[256];
    // No bounds check
    memcpy(buffer, data, size); // Out-of-bounds write if size > 256
}

A patched version would include proper validation:

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

Exploitation & Lab Setup

Red Team

Lab Setup:

• Install Fuji Electric Monitouch V-SFT (vulnerable version) on a Windows VM.
• Create a malicious V10 file using a fuzzer or manual crafting to trigger the overflow.
• Use a debugger (e.g., WinDbg) to identify the exact offset for EIP/RIP control.

Exploitation Steps:

1. Generate a malicious V10 file with a payload that overwrites a return address.
2. Host the file on a web server or send via email.
3. Convince the target user to open the file.
4. Upon execution, the payload runs in the context of the Monitouch V-SFT process.

Note: No public exploit code is available. Red teams should develop custom exploits based on the CWE-787 description.

Blue Team

Detection:

• Monitor for unusual file access patterns to V10 files.
• Use endpoint detection and response (EDR) to detect buffer overflow attempts.
• Enable application whitelisting to prevent untrusted executables from running.

Mitigation:

• Restrict user permissions to prevent arbitrary code execution.
• Use sandboxing or virtualization for opening V10 files.
• Implement network segmentation to limit lateral movement.

Indicators of Compromise (IOCs)

• File Hashes: (None available; generate upon discovery)
• Network Indicators: Connections to known malicious IPs after exploitation.
• Process Anomalies: Monitouch V-SFT process (e.g., V-SFT.exe) crashing or exhibiting abnormal memory usage.
• Registry Changes: Unauthorized modifications to Windows registry keys related to startup or COM objects.
• File System: Creation of unexpected files in temporary directories.

Detection Engineering

YARA Rule

rule CVE_2024_11794_Malicious_V10 {
    meta:
        description = "Detects malicious V10 files exploiting CVE-2024-11794"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-11794"
    strings:
        $magic = { 56 31 30 } // "V10" magic bytes (example)
        $overflow_pattern = { 41 41 41 41 } // Pattern of A's (example)
    condition:
        $magic at 0 and #overflow_pattern > 10
}

Sigma Rule

title: CVE-2024-11794 Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2024-11794 via abnormal V10 file access
author: Valters IT
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: '\V-SFT.exe'
        TargetFilename|endswith: '.v10'
    condition: selection
falsepositives:
    - Legitimate V10 file operations
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11794 Potential Exploit 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: No patch available. Contact Fuji Electric for updates.
• Workaround: Disable automatic parsing of V10 files from untrusted sources. Use file reputation services to scan V10 files before opening.
• User Training: Educate users on the risks of opening unsolicited files.
• Network Controls: Block outbound connections from Monitouch V-SFT processes unless necessary.
• Monitoring: Implement the above detection rules to identify exploitation attempts.

Valters IT
Securing Industrial Environments