CVE-2025-41700

Executive Summary

CVE-2025-41700 is a high-severity vulnerability in the CODESYS development system that allows an unauthenticated attacker to trick a local user into executing arbitrary code by opening a deliberately manipulated CODESYS project file. The vulnerability is classified under CWE-94 (Improper Control of Generation of Code, aka Code Injection) and has a CVSS score of 7.8. The attack vector is local, requiring user interaction, but no authentication is needed. The arbitrary code executes in the context of the logged-in user, potentially leading to full system compromise. No public exploit code or proof-of-concept is available at this time, and the vendor has not released a patch.

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 have physical or remote access to the user's system.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – The victim must open the malicious project file.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): High (H) – Full data access possible.
• Integrity (I): High (H) – Arbitrary code execution allows data modification.
• Availability (A): High (H) – System availability can be compromised.

Threat Level: High. The low attack complexity and lack of authentication make this a significant risk for organizations using CODESYS development systems.

Deep Dive & Mechanics

The vulnerability resides in how the CODESYS development system processes project files. An attacker can craft a malicious .project file that, when opened by a user, triggers arbitrary code execution. The exact mechanism is not publicly disclosed, but it likely involves improper validation of project file contents, such as embedded scripts, macros, or serialized objects that are deserialized without sanitization.

Attack Flow:

1. Delivery: The attacker delivers the malicious project file via email, download, or removable media.
2. Social Engineering: The victim is tricked into opening the file (e.g., "Open this CODESYS project for review").
3. Exploitation: Upon opening, the CODESYS development system processes the file, executing attacker-controlled code.
4. Impact: The code runs with the user's privileges, allowing data theft, malware installation, or lateral movement.

Root Cause: Lack of input validation and code injection prevention in project file parsing.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison is not possible. However, the vulnerable code likely lacks proper sanitization of project file elements. A patched version would implement:

• Input validation: Reject files with unexpected or malicious content.
• Sandboxing: Execute project scripts in a restricted environment.
• Signature verification: Ensure project files are from trusted sources.

Example of vulnerable pseudo-code:

def load_project(file_path):
    data = read_file(file_path)
    # No validation
    execute(data['script'])

Example of patched pseudo-code:

def load_project(file_path):
    data = read_file(file_path)
    if not validate_signature(data):
        raise Exception("Invalid signature")
    if not sanitize_script(data['script']):
        raise Exception("Malicious script detected")
    execute_in_sandbox(data['script'])

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• CODESYS development system installed on a target machine.
• Ability to deliver a malicious .project file to the victim.

Steps:

1. Craft Malicious Project File: Create a CODESYS project file with embedded code that executes a payload (e.g., reverse shell, keylogger).
2. Deliver File: Use phishing email, USB drop, or file-sharing service.
3. Execute: Victim opens the file in CODESYS, triggering the payload.

Example payload (conceptual):

# Embedded in project file
import os
os.system("powershell -enc <base64_encoded_payload>")

Note: No public exploit code is available; this is a conceptual approach.

Blue Team (Defense)

Detection:

• Monitor for unusual CODESYS process behavior (e.g., spawning cmd.exe, PowerShell).
• Use file integrity monitoring to detect modified project files.
• Enable application whitelisting to block untrusted CODESYS executables.

Prevention:

• Restrict execution of CODESYS to authorized users only.
• Use sandboxing or virtual machines for opening project files.
• Implement email filtering to block suspicious attachments.

Hunting:

• Search for recently opened .project files from untrusted sources.
• Analyze CODESYS logs for errors or crashes.

Indicators of Compromise (IOCs)

• File Hashes: (None available; would be generated upon exploit creation)
• Network Indicators: Connections to attacker-controlled IPs (e.g., for reverse shell).
• Process Indicators: CODESYS spawning cmd.exe, powershell.exe, or other interpreters.
• Registry/File System: Unusual files written to %TEMP% or %APPDATA%.
• YARA Rule (see Detection Engineering): Detects malicious project files.

Detection Engineering

YARA Rule

rule CVE_2025_41700_CODESYS_Malicious_Project {
    meta:
        description = "Detects malicious CODESYS project files exploiting CVE-2025-41700"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-41700"
    strings:
        $code_injection = "os.system" nocase
        $code_injection2 = "subprocess" nocase
        $code_injection3 = "exec(" nocase
        $code_injection4 = "eval(" nocase
        $project_magic = { 43 4F 44 45 53 59 53 } // "CODESYS" in hex
    condition:
        $project_magic and (any of ($code_injection*))
}

Sigma Rule

title: CVE-2025-41700 CODESYS Malicious Project File Execution
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects execution of CODESYS development system with potentially malicious project files
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-41700
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\codesys.exe'
        CommandLine|contains: '.project'
    condition: selection
falsepositives:
    - Legitimate use of CODESYS with project files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-41700 CODESYS Malicious Project File Download"; flow:to_server,established; content:"CODESYS"; nocase; content:".project"; nocase; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Auto-Open: Configure CODESYS not to automatically open project files.
2. User Training: Educate users not to open project files from untrusted sources.
3. Application Control: Use AppLocker or similar to restrict CODESYS execution.

Long-Term:

1. Vendor Patch: Monitor CODESYS for a security update and apply immediately.
2. Network Segmentation: Isolate development systems from production networks.
3. File Scanning: Use antivirus/EDR to scan project files for malicious content.

Workaround: If patching is not possible, consider using a dedicated, isolated virtual machine for opening CODESYS project files.

Valters IT