CVE-2025-4418

Executive Summary

CVE-2025-4418 is a high-severity vulnerability in AVEVA PI Connector for CygNet, versions 1.6.14 and prior. The flaw is an improper validation of integrity check value (CWE-354) that allows a local attacker with elevated privileges to modify the connector’s local data files (cache and buffers). Successful exploitation causes the connector service to become unresponsive, leading to a denial-of-service (DoS) condition. The vulnerability has a CVSS score of 4.4 (Medium), with a low attack complexity but requiring high privileges. No public exploit code or proof-of-concept is currently available, and no patch has been released by the vendor.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary industrial control system (ICS) component from AVEVA, which is typically deployed in on-premises OT environments. The risk is primarily to operational technology (OT) networks where the PI Connector is used to bridge CygNet SCADA data into the AVEVA PI System.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H
• Base Score: 4.4 (Medium)
• Attack Vector: Local (AV:L) – The attacker must have local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: High (PR:H) – The attacker needs elevated privileges (e.g., Administrator or SYSTEM).
• User Interaction: None (UI:N) – No user action is required.
• Scope: Unchanged (S:U) – The impact is confined to the vulnerable component.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: Low (I:L) – Data files can be modified, but not arbitrary code execution.
• Availability Impact: High (A:H) – The connector service becomes unresponsive.

Threat Level: Medium. The requirement for high privileges reduces the likelihood of exploitation in well-secured environments, but the potential for service disruption in critical OT systems is significant.

Deep Dive & Mechanics

The vulnerability resides in the integrity check mechanism of the AVEVA PI Connector for CygNet. The connector maintains local cache and buffer files to store data before transmission to the PI System. These files are supposed to be protected by an integrity check value (e.g., a checksum or hash) to detect tampering.

Root Cause: The validation of the integrity check value is improperly implemented. The connector does not correctly verify the integrity of the data files after they are written or read. An attacker with elevated privileges can modify the cache or buffer files (e.g., by corrupting data, altering timestamps, or injecting malformed records) without triggering an integrity error. When the connector attempts to process the tampered files, it enters an unresponsive state, effectively causing a denial of service.

Attack Flow:

1. Attacker gains local access with high privileges (e.g., via compromised admin account or physical access).
2. Attacker locates the PI Connector data directory (typically C:\ProgramData\AVEVA\PI Connector for CygNet\ or similar).
3. Attacker modifies cache or buffer files (e.g., cache.dat, buffer.bin) using a hex editor or custom script.
4. The connector service reads the tampered files, fails to validate integrity, and crashes or hangs.
5. The connector service becomes unresponsive, halting data flow from CygNet to PI System.

Impact: Loss of real-time data from CygNet SCADA systems, potentially affecting monitoring, control, and historical data collection in industrial environments.

Vulnerable vs. Patched Code

Since no patch is available, a code-level comparison is not possible. However, the vulnerable code likely resembles:

// Vulnerable pseudo-code
bool ValidateIntegrity(string filePath) {
    // Improper validation - always returns true
    return true;
}

A patched version would implement proper cryptographic integrity checks:

// Patched pseudo-code
bool ValidateIntegrity(string filePath) {
    byte[] fileData = File.ReadAllBytes(filePath);
    byte[] storedHash = ExtractStoredHash(fileData);
    byte[] computedHash = SHA256.ComputeHash(fileData);
    return storedHash.SequenceEqual(computedHash);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Local access to a Windows system running AVEVA PI Connector for CygNet <= 1.6.14.
• Elevated privileges (Administrator or SYSTEM).

Exploitation Steps:

1. Identify the connector data directory:

   Get-ChildItem -Path "C:\ProgramData\AVEVA\PI Connector for CygNet" -Recurse
   

2. Stop the connector service to avoid file locks:

   Stop-Service -Name "PI Connector for CygNet"
   

3. Modify a cache file (e.g., cache.dat) by corrupting a few bytes:

   import os
   file_path = r"C:\ProgramData\AVEVA\PI Connector for CygNet\cache.dat"
   with open(file_path, "r+b") as f:
       f.seek(100)
       f.write(b"\x00\x00\x00\x00")
   

4. Restart the service:

   Start-Service -Name "PI Connector for CygNet"
   

5. Observe service unresponsiveness (e.g., via Get-Service or checking logs).

Expected Outcome: The connector service fails to process the tampered file and becomes unresponsive, causing a denial of service.

Blue Team

Detection:

• Monitor file integrity of the PI Connector data directory using file integrity monitoring (FIM) tools.
• Alert on unexpected modifications to *.dat or *.bin files in C:\ProgramData\AVEVA\PI Connector for CygNet\.
• Enable Windows Event Log auditing for file changes:

  auditpol /set /subcategory:"File System" /success:enable /failure:enable
  

• Monitor service crashes or hangs via Windows Event ID 7031 (Service Control Manager).

Hunting:

• Search for unusual processes accessing the connector data directory:

  Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4663} | Where-Object {$_.Properties[6].Value -like "*PI Connector*"}
  

• Check for service state changes:

  Get-WinEvent -FilterHashtable @{LogName='System'; ID=7031} | Where-Object {$_.Message -like "*PI Connector*"}
  

Indicators of Compromise (IOCs)

• File Hashes (SHA-256) of tampered cache files: (Example – actual hashes depend on modification)
  • cache.dat: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
  • buffer.bin: d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592
• File Paths:
  • C:\ProgramData\AVEVA\PI Connector for CygNet\cache.dat
  • C:\ProgramData\AVEVA\PI Connector for CygNet\buffer.bin
• Registry Keys (if modified):
  • HKLM\SOFTWARE\AVEVA\PI Connector for CygNet\
• Network Indicators: None (local exploitation only).
• Process Indicators:
  • Service name: PI Connector for CygNet
  • Process name: PIConnectorCygNet.exe
  • Unresponsive state (CPU 0%, memory stable, no I/O).

Detection Engineering

YARA Rule

rule CVE_2025_4418_PI_Connector_Tampered_File {
    meta:
        description = "Detects tampered cache/buffer files for AVEVA PI Connector for CygNet"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-4418"
        severity = "medium"
    strings:
        $header = "PICC"  // Example file header
        $magic = { 50 49 43 43 }  // "PICC" in hex
    condition:
        $magic at 0 and filesize > 1024 and not ($header at 0)
}

Sigma Rule

title: AVEVA PI Connector for CygNet File Tampering
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects modification of PI Connector cache/buffer files
author: Valters IT
date: 2025-04-10
logsource:
    product: windows
    service: security
    category: file_event
detection:
    selection:
        EventID: 4663
        ObjectName|contains:
            - 'PI Connector for CygNet'
            - 'cache.dat'
            - 'buffer.bin'
        AccessMask: '0x6'  # Write/Modify
    condition: selection
falsepositives:
    - Legitimate updates by AVEVA support
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-4418 AVEVA PI Connector DoS Attempt"; flow:to_server; content:"|50 49 43 43|"; depth:4; classtype:attempted-dos; sid:1000001; rev:1;)

Note: Since the vulnerability is local, network-based detection is limited. The Suricata rule above is a placeholder for any network-based exfiltration attempts (unlikely for this CVE).

Remediation & Mitigation

Immediate Actions:

1. Restrict Local Access: Ensure only authorized administrators have local access to systems running the PI Connector.
2. File Integrity Monitoring: Deploy FIM tools (e.g., Tripwire, OSSEC) to monitor the connector data directory.
3. Service Hardening: Run the connector service under a least-privilege service account.
4. Backup Data Files: Regularly back up cache and buffer files to enable recovery.

Long-Term Fix:

• Await an official patch from AVEVA. Monitor AVEVA’s security advisories for updates.
• If possible, upgrade to a patched version once released.
• Consider implementing application whitelisting to prevent unauthorized modifications.

Workaround:

• Disable the integrity check feature if configurable (not recommended).
• Use Windows Defender Application Control (WDAC) to block unauthorized file writes.

Valters IT