CVE-2024-11609

Executive Summary

CVE-2024-11609 is a critical stack-based buffer overflow vulnerability in AutomationDirect C-More EA9 HMI (Human-Machine Interface) panels. The flaw resides in the parsing of EAP9 project files. An attacker can trigger remote code execution by convincing a user to open a malicious EAP9 file or visit a malicious page that loads such a file. The vulnerability is unpatched at the time of analysis, and no public proof-of-concept (PoC) code or exploit is available. The CVSS score of 7.8 reflects the high impact on confidentiality, integrity, and availability, but the requirement for user interaction lowers the base score.

This vulnerability is not related to any open-source package ecosystem (NPM, PyPI, Go, Ruby) and is specific to the proprietary AutomationDirect C-More EA9 software.

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 (AV): Local (L) – The attacker must deliver a malicious file to the target system.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – The victim must open the malicious file.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): High (H) – Full data compromise possible.
• Integrity (I): High (H) – Full control over data.
• Availability (A): High (H) – Potential denial of service or full system compromise.

Threat Level: High. Although user interaction is required, the lack of a patch and the potential for full code execution in the context of the current process (likely with user-level privileges) makes this a serious threat for industrial control system (ICS) environments.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow (CWE-121) in the EAP9 file parser of AutomationDirect C-More EA9 software. The EAP9 file format is used to store HMI project configurations, including screen layouts, tags, and communication settings.

Root Cause: The parser fails to validate the length of user-supplied data before copying it to a fixed-length stack buffer. When a specially crafted EAP9 file is opened, an oversized field overwrites the stack, corrupting the return address and other critical data.

Exploitation Flow:

1. An attacker crafts a malicious EAP9 file containing a payload that exceeds the expected buffer size.
2. The victim opens the file using the C-More EA9 software (e.g., via email attachment, web download, or USB drive).
3. The parser copies the oversized data into a stack buffer, overwriting the saved return address.
4. When the function returns, execution jumps to an address controlled by the attacker (typically a ROP chain or shellcode).
5. The attacker gains code execution in the context of the current user.

Impact: Full compromise of the HMI workstation, which could lead to manipulation of industrial processes, data exfiltration, or lateral movement within the OT network.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable code pattern is typical:

Vulnerable (C-like pseudocode):

void ParseEAP9Field(char *input) {
    char buffer[256];
    // No length check
    strcpy(buffer, input);  // Stack overflow if input > 255 bytes
}

Patched (hypothetical):

void ParseEAP9Field(char *input) {
    char buffer[256];
    // Safe copy with length limit
    strncpy(buffer, input, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
}

The fix would involve replacing unsafe functions like strcpy with bounded alternatives such as strncpy or using modern C++ string classes.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• AutomationDirect C-More EA9 software (any version)
• A Windows VM for testing
• Python 3.x with struct and socket libraries

Lab Setup:

1. Install the C-More EA9 software on a Windows 10/11 VM.
2. Disable Windows Defender or add an exclusion for the test directory.
3. Use a debugger (e.g., x64dbg) to analyze the crash.

Exploit Development Steps:

1. Fuzzing: Use a fuzzer (e.g., boofuzz) to send malformed EAP9 files to the parser and identify the crash offset.
2. Offset Determination: Use a pattern string (e.g., pattern_create.rb from Metasploit) to find the exact offset that overwrites the return address.
3. Overwrite EIP: Craft a payload that overwrites the return address with a controlled value.
4. Bypass Protections: If DEP/ASLR are enabled, use ROP chains to disable DEP or call VirtualProtect.
5. Shellcode: Generate shellcode (e.g., reverse shell) using msfvenom.

Example Python skeleton (no public PoC):

import struct

# Offset to EIP (example, adjust via fuzzing)
offset = 260
# ROP gadget address (example)
rop_gadget = 0x00401234
# Shellcode (placeholder)
shellcode = b"\x90" * 100  # NOP sled + actual shellcode

payload = b"A" * offset
payload += struct.pack("<I", rop_gadget)
payload += shellcode

# Write to file
with open("malicious.eap9", "wb") as f:
    f.write(payload)

Delivery: Email the file to the victim or host it on a malicious website.

Blue Team (Defense)

Detection:

• Monitor for unusual EAP9 file creation/modification in shared directories.
• Use endpoint detection and response (EDR) to detect stack-based buffer overflow behavior (e.g., strcpy to stack buffer).
• Enable Windows Defender Exploit Guard (ASR rules) to block Office/script files from spawning child processes.

Hunting:

• Search for EAP9 files with abnormally large sizes or suspicious strings.
• Look for processes (e.g., EAP9.exe) crashing with access violations.

Mitigation:

• Restrict execution of C-More EA9 software to authorized users only.
• Use application whitelisting (e.g., AppLocker) to prevent untrusted executables.
• Isolate HMI workstations from the internet and corporate network.

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2024_11609_Malicious_EAP9 {
    meta:
        description = "Detects malicious EAP9 files exploiting CVE-2024-11609"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-11609"
    strings:
        $magic = { 45 41 50 39 } // "EAP9" magic bytes
        $overflow = { 41 41 41 41 41 41 41 41 } // Pattern of 'A's (example)
        $shellcode = { 90 90 90 90 90 90 90 90 } // NOP sled (example)
    condition:
        $magic at 0 and ( #overflow > 100 or #shellcode > 50 )
}

Sigma Rule

title: C-More EA9 EAP9 File Parsing Buffer Overflow
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects crashes or suspicious behavior from C-More EA9 software when opening EAP9 files.
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-11609
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\EAP9.exe'
        CommandLine|contains: '.eap9'
    condition: selection
falsepositives:
    - Legitimate use of EAP9 files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-11609 C-More EA9 EAP9 File Download"; flow:to_server,established; content:"EAP9"; nocase; fileext:"eap9"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate: Disconnect C-More EA9 workstations from the internet and untrusted networks.
2. Restrict: Use application whitelisting to allow only trusted executables.
3. Monitor: Enable detailed logging for process creation and file access events.
4. Educate: Train users not to open EAP9 files from untrusted sources.

Long-Term Fix:

• Await an official patch from AutomationDirect. Contact their support for a timeline.
• If possible, migrate to a different HMI platform that is actively maintained.

Workaround:

• Use a file scanner that can detect oversized fields in EAP9 files (custom YARA rule above).
• Run the C-More EA9 software in a sandboxed environment (e.g., Windows Sandbox).

Valters IT