What is Improper Neutralization of Wildcards (CWE-155)?

TL;DR: Improper Neutralization of Wildcards or Matching Symbols (CWE-155) is a vulnerability that occurs when a product fails to neutralize special elements in input from an upstream component.

What is Improper Neutralization of Wildcards or Matching Symbols?

Improper Neutralization of Wildcards or Matching Symbols (CWE-155) is a type of injection vulnerability that occurs when a product receives input from an upstream component but fails to neutralize special elements that could be interpreted as wildcards or matching symbols when sent to a downstream component. As defined by the MITRE Corporation under CWE-155; it is not directly mapped to a specific OWASP Top 10:2025 category.

Quick Summary

Improper Neutralization of Wildcards or Matching Symbols (CWE-155) is a significant security risk that can lead to unauthorized access, data tampering, and system compromise. It is essential to prevent CWE-155 by implementing robust input validation and sanitization mechanisms.

Jump to: Quick Summary · Improper Neutralization of Wildcards or Matching Symbols Overview · How Improper Neutralization of Wildcards or Matching Symbols Works · Business Impact of Improper Neutralization of Wildcards or Matching Symbols · Improper Neutralization of Wildcards or Matching Symbols Attack Scenario · How to Detect Improper Neutralization of Wildcards or Matching Symbols · How to Fix Improper Neutralization of Wildcards or Matching Symbols · Framework-Specific Fixes for Improper Neutralization of Wildcards or Matching Symbols · How to Ask AI to Check Your Code for Improper Neutralization of Wildcards or Matching Symbols · Improper Neutralization of Wildcards or Matching Symbols Best Practices Checklist · Improper Neutralization of Wildcards or Matching Symbols FAQ · Vulnerabilities Related to Improper Neutralization of Wildcards or Matching Symbols · References · Scan Your Own Site

Improper Neutralization of Wildcards or Matching Symbols Overview

What: Improper Neutralization of Wildcards or Matching Symbols (CWE-155) is a type of injection vulnerability that occurs when a product receives input from an upstream component but fails to neutralize special elements that could be interpreted as wildcards or matching symbols when sent to a downstream component.

Why it matters: CWE-155 can lead to unauthorized access, data tampering, and system compromise, resulting in significant financial losses, reputational damage, and compliance issues.

Where it occurs: CWE-155 typically occurs in web applications, web services, and APIs that receive input from upstream components but fail to neutralize special elements.

Who is affected: Any organization or individual using a product vulnerable to CWE-155 can be affected by this vulnerability.

Who is NOT affected: Applications that never construct paths/queries/commands from external input are not typically affected by CWE-155.

How Improper Neutralization of Wildcards or Matching Symbols Works

Root Cause

The root cause of CWE-155 is the failure to neutralize special elements in input from an upstream component.

Attack Flow

1. An attacker sends malicious input to a web application or API.
2. The product receives the input but fails to neutralize special elements, allowing them to be interpreted as wildcards or matching symbols.
3. The downstream component processes the input, leading to unauthorized access, data tampering, and system compromise.

Prerequisites to Exploit

• Malicious input must reach a vulnerable sink (e.g., database query, file path).
• Special elements in the input must not be properly neutralized.

Vulnerable Code

import os

path = request.form['path']
os.chdir(path)

This code is vulnerable because it fails to neutralize special elements in the path variable.

Secure Code

import os

path = request.form['path']
if not os.path.abspath(path).startswith(base_dir):
    raise ValueError("Invalid path")
else:
    os.chdir(path)

This secure code checks if the path variable is within an allowed base directory before processing it.

Business Impact of Improper Neutralization of Wildcards or Matching Symbols

Confidentiality: CWE-155 can lead to unauthorized access to sensitive data, resulting in confidentiality breaches.

Integrity: CWE-155 can allow attackers to tamper with data, leading to integrity compromises.

Availability: CWE-155 can cause system compromise, resulting in downtime and loss of availability.

Real-world business consequences:

• Financial losses due to data breaches or system compromise.
• Reputational damage due to public disclosure of vulnerabilities.
• Compliance issues due to failure to meet regulatory requirements.

Improper Neutralization of Wildcards or Matching Symbols Attack Scenario

1. An attacker sends malicious input to a web application or API.
2. The product receives the input but fails to neutralize special elements, allowing them to be interpreted as wildcards or matching symbols.
3. The downstream component processes the input, leading to unauthorized access, data tampering, and system compromise.

How to Detect Improper Neutralization of Wildcards or Matching Symbols

Manual Testing

• Review code for potential CWE-155 vulnerabilities.
• Test input validation and sanitization mechanisms.
• Verify that special elements are properly neutralized.

Automated Scanners (SAST/DAST)

• Use SAST tools to identify potential CWE-155 vulnerabilities in code.
• Use DAST tools to simulate attacks on web applications or APIs.

PenScan Detection

PenScan’s automated scanning engines actively test for CWE-155 vulnerabilities.

False Positive Guidance

When reviewing findings, consider the context of the input and the downstream component. CWE-155 can be difficult to detect due to its reliance on specific input patterns.

How to Fix Improper Neutralization of Wildcards or Matching Symbols

• Implement robust input validation and sanitization mechanisms.
• Escape special characters in input.
• Use secure error handling mechanisms.

Framework-Specific Fixes for Improper Neutralization of Wildcards or Matching Symbols

Java

import java.util.regex.Pattern;

String path = request.getParameter("path");
if (!Pattern.matches("^/[^/]+$", path)) {
    throw new ServletException("Invalid path");
}

This code uses a regular expression to validate the path variable.

Node.js

const express = require('express');
const app = express();

app.get('/path', (req, res) => {
  const path = req.query.path;
  if (!/^[^/]+$/.test(path)) {
    return res.status(400).send("Invalid path");
  }
});

This code uses a regular expression to validate the path variable.

Python/Django

import re

def get_path(request):
    path = request.GET.get('path')
    if not re.match(r'^[^/]+$', path):
        raise ValueError("Invalid path")
    return path

This code uses a regular expression to validate the path variable.

PHP

<?php
$path = $_GET['path'];
if (!preg_match('/^[^/]+$/', $path)) {
    header('HTTP/1.1 400 Bad Request');
    exit;
}
?>

This code uses a regular expression to validate the path variable.

How to Ask AI to Check Your Code for Improper Neutralization of Wildcards or Matching Symbols

You can use AI-powered coding assistants to review your code for potential CWE-155 vulnerabilities and provide recommendations for remediation. Here is an example prompt you can copy-paste:

“Review the following Python code block for potential CWE-155 Improper Neutralization of Wildcards or Matching Symbols vulnerabilities and rewrite it using input validation and sanitization mechanisms: [paste code here]”

Improper Neutralization of Wildcards or Matching Symbols Best Practices Checklist

✅ Implement robust input validation and sanitization mechanisms. ✅ Escape special characters in input. ✅ Use secure error handling mechanisms.

Improper Neutralization of Wildcards or Matching Symbols FAQ

How does Improper Neutralization of Wildcards or Matching Symbols occur?

Improper Neutralization of Wildcards or Matching Symbols occurs when a product receives input from an upstream component but fails to neutralize special elements that could be interpreted as wildcards or matching symbols when sent to a downstream component.

What is the impact of CWE-155 on business operations?

CWE-155 can lead to unauthorized access, data tampering, and system compromise, resulting in significant financial losses, reputational damage, and compliance issues.

How can I detect CWE-155 vulnerabilities in my application?

You can use manual testing, automated scanners (SAST/DAST), or PenScan’s detection capabilities to identify CWE-155 vulnerabilities.

What are the best practices for preventing CWE-155?

Use input validation and sanitization, escape special characters, and implement robust error handling mechanisms to prevent CWE-155.

Can AI help me detect and fix CWE-155 vulnerabilities in my code?

Yes, you can use AI-powered coding assistants to review your code for potential CWE-155 vulnerabilities and provide recommendations for remediation.

What are the related CWEs to CWE-155?

The related CWEs to CWE-155 include CWE-138 (Improper Neutralization of Special Elements) as a parent weakness.markdown

Vulnerabilities Related to Improper Neutralization of Wildcards or Matching Symbols

References

• MITRE CWE-155
• NIST NVD

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find Improper Neutralization of Wildcards or Matching Symbols and other risks before an attacker does.