CVE-2024-11798

Executive Summary

CVE-2024-11798 is a critical out-of-bounds write vulnerability in Fuji Electric Monitouch V-SFT, specifically during the parsing of X1 files. The flaw allows remote code execution (RCE) in the context of the current process, requiring user interaction (e.g., visiting a malicious page or opening a malicious file). 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/SCADA configuration. No public exploit or patch is currently available, but the vulnerability is weaponizable via crafted X1 files.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Local (AV:L) – requires user to open a file.
• Attack Complexity (AC): Low (AC:L) – no special conditions.
• Privileges Required (PR): None (PR:N) – no authentication needed.
• User Interaction (UI): Required (UI:R) – victim must open malicious file.
• Scope (S): Unchanged (S:U) – vulnerability does not cross trust boundaries.
• Confidentiality (C): High (C:H) – full data access possible.
• Integrity (I): High (I:H) – arbitrary code execution.
• Availability (A): High (A:H) – potential for denial of service or full compromise.

Threat Level: Critical – exploitation leads to full system compromise in the context of the current user.

Deep Dive & Mechanics

The vulnerability resides in the parsing logic of X1 files within Fuji Electric Monitouch V-SFT. The software fails to validate user-supplied data properly, leading to a write past the end of an allocated buffer (out-of-bounds write). This memory corruption can be leveraged by an attacker to overwrite critical data structures, such as function pointers or return addresses, enabling arbitrary code execution.

Root Cause: Lack of bounds checking when processing X1 file fields. An attacker can craft an X1 file with oversized or malformed data that triggers a buffer overflow during parsing.

Attack Vector: The attacker delivers a malicious X1 file via email, download, or USB. When the victim opens the file in V-SFT, the overflow occurs, and the attacker’s shellcode executes.

Vulnerable vs. Patched Code

No official patch is available. The vulnerable code likely resides in the X1 file parser module. A patched version would include proper bounds checking and input validation.

Vulnerable Code (Conceptual):

void parse_x1_field(char *buffer, int size) {
    char local_buf[256];
    memcpy(local_buf, buffer, size); // No size check – overflow if size > 256
}

Patched Code (Conceptual):

void parse_x1_field(char *buffer, int size) {
    char local_buf[256];
    if (size > 256) {
        // Handle error or truncate
        return;
    }
    memcpy(local_buf, buffer, size);
}

Exploitation & Lab Setup

Red Team (Offensive)

Lab Environment:

• Windows 10/11 VM with Fuji Electric Monitouch V-SFT installed.
• Python3 for crafting malicious X1 files.

Exploit Steps:

1. Create a malicious X1 file with a buffer overflow payload.
2. Deliver the file to the victim (e.g., via phishing email).
3. Victim opens the file in V-SFT, triggering the overflow.
4. Payload executes, providing a reverse shell or arbitrary code execution.

Example Payload (Python):

import struct

# Craft malicious X1 file
payload = b"A" * 256  # Overflow buffer
payload += struct.pack("<I", 0xdeadbeef)  # Overwrite return address
# Add shellcode here
with open("malicious.x1", "wb") as f:
    f.write(payload)

Blue Team (Defensive)

Detection:

• Monitor for unusual X1 file access or crashes in V-SFT.
• Use endpoint detection and response (EDR) to detect memory corruption events.
• Block X1 files from untrusted sources via email or web gateways.

Hunting:

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

Indicators of Compromise (IOCs)

• File Hashes: (Example – replace with actual when available)
  • malicious.x1 – SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network: Outbound connections from V-SFT process to unknown IPs.
• Process: V-SFT.exe crashing or spawning cmd.exe / powershell.exe.
• Registry: Unusual modifications under HKCU\Software\Fuji Electric.

Detection Engineering

YARA Rule

rule CVE_2024_11798_X1_Overflow {
    meta:
        description = "Detects malicious X1 files targeting CVE-2024-11798"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $x1_magic = { 58 31 00 } // "X1\0" magic bytes
        $overflow = { 41 41 41 41 } // "AAAA" pattern
    condition:
        $x1_magic at 0 and #overflow > 10
}

Sigma Rule

title: Fuji Electric V-SFT X1 File Overflow
id: 7a8b3c4d-5e6f-7890-abcd-ef1234567890
status: experimental
description: Detects V-SFT crashes or suspicious file access
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: 'V-SFT.exe'
        CommandLine|contains: '.x1'
    condition: selection
falsepositives:
    - Legitimate X1 file usage
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11798 X1 File Download"; flow:to_server,established; content:"X1"; nocase; fileext:"x1"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Disable or restrict opening X1 files from untrusted sources.
• Workaround: Use application whitelisting to block V-SFT from executing untrusted files.
• Long-term: Apply vendor patch when available. Monitor Fuji Electric advisories.
• Compensating Controls: Deploy endpoint protection with behavioral analysis to detect memory corruption.

Valters IT
Securing Industrial Environments