What is Improper Neutralization of Section (CWE-145)?

TL;DR: Improper Neutralization of Section Delimiters (CWE-145) occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes special elements that could be interpreted as section delimiters when sent to a downstream component. To fix CWE-145 vulnerabilities, you should develop a comprehensive input validation strategy that includes both allowlists and denylists, as well as properly encode special characters.

What is Improper Neutralization of Section Delimiters?

Improper Neutralization of Section Delimiters (CWE-145) is a type of Security Misconfiguration vulnerability that occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes special elements that could be interpreted as section delimiters when sent to a downstream component. As defined by the MITRE Corporation under CWE-145, and classified by the OWASP Foundation under A9:2021 - Security Misconfiguration, this vulnerability can have significant business impacts.

Quick Summary

Improper Neutralization of Section Delimiters (CWE-145) is a critical security vulnerability that can lead to unexpected state, resulting in various business impacts such as data tampering or unauthorized access. It is essential for developers and organizations to understand the root cause, attack flow, and potential mitigations for this weakness.

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

Improper Neutralization of Section Delimiters Overview

What: CWE-145 occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes special elements that could be interpreted as section delimiters when sent to a downstream component.

Why it matters: CWE-145 can lead to unexpected state, which can result in various business impacts such as data tampering or unauthorized access.

Where it occurs: CWE-145 typically occurs in web applications and services that receive input from upstream components.

Who is affected: CWE-145 affects organizations and developers who do not properly neutralize section delimiters in their products.

Who is NOT affected: CWE-145 does not affect organizations and developers who have implemented comprehensive input validation strategies, including both allowlists and denylists, as well as proper encoding of special characters.

How Improper Neutralization of Section Delimiters Works

Root Cause

The root cause of CWE-145 is the failure to neutralize or incorrect neutralization of special elements that could be interpreted as section delimiters when sent to a downstream component.

Attack Flow

1. An attacker sends input to an upstream component.
2. The upstream component fails to properly neutralize or incorrectly neutralizes special elements in the input.
3. The downstream component interprets the special elements as section delimiters, leading to unexpected state.

Prerequisites to Exploit

• The upstream component must receive input from a malicious source.
• The downstream component must interpret the special elements as section delimiters.

Vulnerable Code

import os

input_string = request.form['input']
os.chdir(input_string)

This code is vulnerable because it fails to properly neutralize special characters in the input string, which could be interpreted as section delimiters by the downstream component.

Secure Code

import os

input_string = request.form['input']
encoded_input = urllib.parse.quote_plus(input_string)
os.chdir(encoded_input)

This code is secure because it properly encodes special characters in the input string using urllib.parse.quote_plus, preventing them from being interpreted as section delimiters by the downstream component.

Business Impact of Improper Neutralization of Section Delimiters

The primary consequence of CWE-145 is unexpected state, which can lead to various business impacts such as data tampering or unauthorized access. The CIA triad is affected as follows:

• Confidentiality: Data tampering or unauthorized access to sensitive information.
• Integrity: Modification of data or system configuration.
• Availability: Disruption of service or system downtime.

The following are some real-world business consequences of CWE-145:

• Financial losses due to data tampering or unauthorized access.
• Compliance issues due to failure to protect sensitive information.
• Reputation damage due to public disclosure of security vulnerabilities.

Improper Neutralization of Section Delimiters Attack Scenario

1. An attacker sends input to an upstream component.
2. The upstream component fails to properly neutralize or incorrectly neutralizes special elements in the input.
3. The downstream component interprets the special elements as section delimiters, leading to unexpected state.
4. The attacker exploits the unexpected state to gain unauthorized access or modify sensitive data.

How to Detect Improper Neutralization of Section Delimiters

Manual Testing

• Review code for potential CWE-145 vulnerabilities.
• Test input validation strategies, including allowlists and denylists.
• Verify proper encoding of special characters.

Automated Scanners (SAST / DAST)

• Static analysis tools can detect potential CWE-145 vulnerabilities in code.
• Dynamic analysis tools can simulate attacks to identify CWE-145 vulnerabilities.

PenScan Detection

PenScan’s automated scanning engines actively test for CWE-145 vulnerabilities, ensuring your website is secure and compliant.

False Positive Guidance

When reviewing findings from manual testing or automated scanners, consider the following:

• CWE-145 may be reported as a false positive if the input validation strategy includes both allowlists and denylists.
• CWE-145 may be reported as a false positive if special characters are properly encoded in the input string.

How to Fix Improper Neutralization of Section Delimiters

To fix CWE-145 vulnerabilities, follow these steps:

• Develop comprehensive input validation strategies that include both allowlists and denylists.
• Properly encode special characters in input strings using urllib.parse.quote_plus.
• Regularly review and update input validation strategies to ensure they remain effective.

Framework-Specific Fixes for Improper Neutralization of Section Delimiters

Java

import java.net.URLEncoder;

String encodedInput = URLEncoder.encode(input, "UTF-8");

Node.js

const querystring = require('querystring');

String encodedInput = querystring.escape(input);

Python/Django

from urllib.parse import quote_plus

encoded_input = quote_plus(input)

PHP

<?php
$input = $_POST['input'];
$encoded_input = urlencode($input);
?>

How to Ask AI to Check Your Code for Improper Neutralization of Section Delimiters

Review the following Python code block for potential CWE-145 vulnerabilities and rewrite it using proper encoding:

import os

input_string = request.form['input']
os.chdir(input_string)

Rewrite the code as follows:

import os
from urllib.parse import quote_plus

input_string = request.form['input']
encoded_input = quote_plus(input_string)
os.chdir(encoded_input)

Improper Neutralization of Section Delimiters Best Practices Checklist

✅ Develop comprehensive input validation strategies that include both allowlists and denylists. ✅ Properly encode special characters in input strings using urllib.parse.quote_plus. ✅ Regularly review and update input validation strategies to ensure they remain effective.

Improper Neutralization of Section Delimiters FAQ

How does Improper Neutralization of Section Delimiters occur?

Improper Neutralization of Section Delimiters occurs when a product receives input from an upstream component but fails to neutralize or incorrectly neutralizes special elements that could be interpreted as section delimiters when sent to a downstream component.

What are the consequences of Improper Neutralization of Section Delimiters?

The primary consequence of Improper Neutralization of Section Delimiters is unexpected state, which can lead to various business impacts such as data tampering or unauthorized access.

How do I detect Improper Neutralization of Section Delimiters in my code?

You can use manual testing and automated scanning tools like PenScan to detect CWE-145 vulnerabilities in your code.

What are the best practices for preventing Improper Neutralization of Section Delimiters?

To prevent Improper Neutralization of Section Delimiters, you should develop a comprehensive input validation strategy that includes both allowlists and denylists, as well as properly encode special characters.

Can AI help me identify CWE-145 vulnerabilities in my code?

Yes, AI-powered coding assistants can review your code for potential CWE-145 vulnerabilities and provide recommendations for remediation.

What are the related weaknesses to Improper Neutralization of Section Delimiters?

The related weaknesses to Improper Neutralization of Section Delimiters include CWE-140 (Improper Neutralization of Delimiters) and CWE-93 (Improper Neutralization of CRLF Sequences).

How do I fix CWE-145 vulnerabilities in my code?

To fix CWE-145 vulnerabilities, you should follow the remediation steps outlined in the Potential_Mitigations data provided.

Vulnerabilities Related to Improper Neutralization of Section Delimiters

References

• [1] MITRE Corporation. (n.d.). CWE-145: Improper Neutralization of Section Delimiters.
• [3] NIST National Vulnerability Database. (n.d.). CWE-145.
• MITRE - CWE-145
• 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 Section Delimiters and other risks before an attacker does.