CVE-2024-11793

Executive Summary

CVE-2024-11793 is a critical out-of-bounds write vulnerability in Fuji Electric Monitouch V-SFT, specifically within the parsing of V9C files. This flaw allows remote attackers to execute arbitrary code on affected installations, but requires user interaction (the target must open a malicious V9C file or visit a malicious page). The vulnerability has a CVSS score of 7.8 (High) and is classified under CWE-787 (Out-of-bounds Write). No public exploit code or patch details are currently available, and the EPSS score is 0.0%, indicating low exploitation activity at this time. The vulnerability was reported via ZDI-CAN-24503.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Attack Vector: Local (AV:L) – requires user interaction to open a malicious file.
• Attack Complexity: Low (AC:L) – no special conditions needed.
• Privileges Required: None (PR:N) – attacker does not need prior access.
• User Interaction: Required (UI:R) – victim must open the file.
• Scope: Unchanged (S:U) – vulnerability does not affect other components.
• Confidentiality Impact: High (C:H) – potential data exposure.
• Integrity Impact: High (I:H) – arbitrary code execution.
• Availability Impact: High (A:H) – potential system crash or compromise.

Threat Level: High. Although no public exploit exists, the vulnerability is remotely exploitable with user interaction and can lead to full system compromise.

Deep Dive & Mechanics

The vulnerability resides in the parsing logic of V9C files within Fuji Electric Monitouch V-SFT (version V9C). The specific flaw is an out-of-bounds write: the software fails to properly validate user-supplied data when processing a V9C file, allowing an attacker to write data beyond the allocated buffer boundary. This can corrupt adjacent memory and lead to arbitrary code execution in the context of the current process.

Root Cause: Lack of proper bounds checking on user-supplied data during V9C file parsing.

Attack Vector: Remote, but requires user interaction (opening a malicious file or visiting a malicious page that triggers file download/opening).

Impact: Successful exploitation allows an attacker to execute arbitrary code with the privileges of the user running the V-SFT application, potentially leading to full system compromise.

Vulnerable vs. Patched Code

No patch details are available. The vulnerable code is in the V9C file parsing routine. A patched version would include proper bounds checking to prevent writing past the end of allocated buffers.

Vulnerable Code (Conceptual):

void parse_v9c_file(char *data, size_t size) {
    char buffer[256];
    // No bounds check
    memcpy(buffer, data, size); // Out-of-bounds write if size > 256
}

Patched Code (Conceptual):

void parse_v9c_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

Prerequisites:

• Fuji Electric Monitouch V-SFT V9C installed on a target system.
• Ability to deliver a malicious V9C file to the target (e.g., via email, web download, or USB).

Exploitation Steps:

1. Craft a malicious V9C file with a payload that triggers the out-of-bounds write.
2. Deliver the file to the target (e.g., via phishing email with attachment).
3. When the target opens the file in V-SFT, the exploit triggers arbitrary code execution.

Note: No public exploit code is available. The following is a conceptual example:

# Conceptual exploit (not functional)
import struct

def create_malicious_v9c():
    payload = b"A" * 300  # Overflow buffer
    # Craft V9C header and payload
    with open("malicious.v9c", "wb") as f:
        f.write(payload)

create_malicious_v9c()

Blue Team

Detection:

• Monitor for unusual V9C file downloads or openings.
• Use endpoint detection and response (EDR) to detect abnormal process behavior (e.g., V-SFT crashing or spawning child processes).
• Implement file integrity monitoring for V-SFT binaries.

Mitigation:

• Restrict execution of V-SFT to trusted users only.
• Use application whitelisting to prevent unauthorized software.
• Educate users about phishing risks and malicious file attachments.

Indicators of Compromise (IOCs)

• File Hashes: (None available; would be generated from malicious V9C files)
• Network Indicators: Connections to known malicious IPs or domains (if payload calls back).
• Process Anomalies: V-SFT process (e.g., V-SFT.exe) crashing or exhibiting unusual memory access patterns.
• Registry/File System: Creation of unexpected files or registry keys in the user context.

Detection Engineering

YARA Rule

rule CVE_2024_11793_Malicious_V9C {
    meta:
        description = "Detects malicious V9C files exploiting CVE-2024-11793"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-11793"
    strings:
        $v9c_header = "V9C" ascii wide nocase
        $overflow_pattern = { 41 41 41 41 41 41 41 41 } // Pattern of 'A's
    condition:
        $v9c_header and #overflow_pattern > 10
}

Sigma Rule

title: CVE-2024-11793 Exploitation Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects potential exploitation of CVE-2024-11793 via V9C file parsing
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: 'V-SFT.exe'
        CommandLine|contains: '.v9c'
    condition: selection
falsepositives:
    - Legitimate use of V-SFT with V9C files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11793 V9C File Download"; flow:to_server,established; content:"V9C"; nocase; fileext:"v9c"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

• No patch available. Disable or restrict use of Fuji Electric Monitouch V-SFT V9C until a patch is released.
• Implement strict application whitelisting to prevent execution of V-SFT.
• Use network segmentation to limit exposure.

Long-term:

• Monitor vendor advisories for patch updates.
• Consider migrating to alternative software if no patch is provided.
• Enhance user awareness training to avoid opening untrusted files.

Workarounds:

• Use file reputation services to block known malicious V9C files.
• Enable Windows Defender Exploit Guard or similar ASLR mitigations.

Valters IT
Securing Digital Frontiers