What is Signed to Unsigned Conversion Error (CWE-195)?

TL;DR: Signed to Unsigned Conversion Error (CWE-195) occurs when a signed primitive is cast to an unsigned primitive, producing unexpected values if the value of the signed primitive can’t be represented using an unsigned primitive. Use unsigned primitives, validate input values, and check for overflow conditions to prevent this vulnerability.

At-a-Glance Table

What is Signed to Unsigned Conversion Error?

Signed to Unsigned Conversion Error (CWE-195) is a type of CWE that occurs when a signed primitive is cast to an unsigned primitive, producing unexpected values if the value of the signed primitive can’t be represented using an unsigned primitive. As defined by the MITRE Corporation under CWE-195.

Quick Summary

Signed to Unsigned Conversion Error (CWE-195) is a vulnerability that occurs when a signed primitive is cast to an unsigned primitive, producing unexpected values if the value of the signed primitive can’t be represented using an unsigned primitive. This vulnerability can lead to Unexpected State and Integrity issues, compromising the security and reliability of your application.

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

Signed to Unsigned Conversion Error Overview

What

Signed to Unsigned Conversion Error (CWE-195) occurs when a signed primitive is cast to an unsigned primitive, producing unexpected values if the value of the signed primitive can’t be represented using an unsigned primitive.

Why it matters

This vulnerability can lead to Unexpected State and Integrity issues, compromising the security and reliability of your application.

Where it occurs

Signed to Unsigned Conversion Error (CWE-195) can occur in various programming languages, including C, C++, Java, Python, Node.js, and PHP.

Who is affected

Developers who use signed primitives without considering their limitations are at risk of introducing this vulnerability into their code.

Who is NOT affected

Applications that exclusively use unsigned primitives or do not perform arithmetic operations on signed values are not vulnerable to Signed to Unsigned Conversion Error (CWE-195).

How Signed to Unsigned Conversion Error Works

Root Cause

The root cause of Signed to Unsigned Conversion Error (CWE-195) is the casting of a signed primitive to an unsigned primitive, which can produce unexpected values if the value of the signed primitive cannot be represented using an unsigned primitive.

Attack Flow

1. The attacker inputs a large negative number into a function that expects an unsigned integer.
2. The function casts the input to an unsigned integer, causing it to wrap around and become a large positive number.
3. The application uses this incorrect value, leading to Unexpected State and Integrity issues.

Prerequisites to Exploit

• The attacker must be able to input values into the application’s functions.
• The application must use signed primitives without considering their limitations.

Vulnerable Code

int main() {
    unsigned int x = (unsigned int) -1; // Signed primitive cast to unsigned primitive
    return 0;
}

This code demonstrates a vulnerable scenario where a signed integer is cast to an unsigned integer, producing unexpected values if the value of the signed integer cannot be represented using an unsigned integer.

Secure Code

int main() {
    unsigned int x = -1; // Use unsigned primitive directly
    return 0;
}

This code demonstrates a secure scenario where an unsigned integer is used directly, avoiding the casting issue that leads to Signed to Unsigned Conversion Error (CWE-195).

Business Impact of Signed to Unsigned Conversion Error

Confidentiality

Signed to Unsigned Conversion Error (CWE-195) can lead to Unexpected State and Integrity issues, compromising the security and reliability of your application. This can result in unauthorized access to sensitive data or modifications to critical systems.

Integrity

The vulnerability can also cause data corruption or tampering, leading to financial losses, compliance issues, and reputational damage.

Availability

In extreme cases, Signed to Unsigned Conversion Error (CWE-195) can lead to system crashes or downtime, compromising the availability of your application.

Signed to Unsigned Conversion Error Attack Scenario

1. The attacker inputs a large negative number into a function that expects an unsigned integer.
2. The function casts the input to an unsigned integer, causing it to wrap around and become a large positive number.
3. The application uses this incorrect value, leading to Unexpected State and Integrity issues.

How to Detect Signed to Unsigned Conversion Error

Manual Testing

• Review your code for signed primitive casting operations.
• Use tools like Valgrind or AddressSanitizer to detect potential errors.

Automated Scanners (SAST / DAST)

• Static analysis tools can identify potential issues with signed primitive casting.
• Dynamic analysis tools can simulate attacks and detect vulnerabilities.

PenScan Detection

PenScan’s scanner engines actively test for this issue, providing detailed reports and recommendations for remediation.

False Positive Guidance

When reviewing the results of automated scanners or manual testing, consider the following:

• Check if the input values are within the expected range.
• Verify that the application uses unsigned primitives directly instead of casting signed primitives.

How to Fix Signed to Unsigned Conversion Error

• Use unsigned primitives directly instead of casting signed primitives.
• Validate input values to ensure they are within the expected range.
• Check for overflow conditions and handle them accordingly.

Framework-Specific Fixes for Signed to Unsigned Conversion Error

C and C++

Use unsigned integers directly instead of casting signed integers:

unsigned int x = -1;

Java

Use int or long types instead of Integer or Long objects, which can be cast to int or long:

int x = -1;

Python/Django

Use int type instead of str or float types, which can be cast to int:

x = -1

PHP

Use int type instead of string or float types, which can be cast to int:

$x = -1;

How to Ask AI to Check Your Code for Signed to Unsigned Conversion Error

You can use AI coding assistants to review your code for potential CWE-195 Signed to Unsigned Conversion Error vulnerabilities and rewrite it using primary fix techniques.

Signed to Unsigned Conversion Error Best Practices Checklist

✅ Use unsigned primitives directly instead of casting signed primitives. ✅ Validate input values to ensure they are within the expected range. ✅ Check for overflow conditions and handle them accordingly.

Signed to Unsigned Conversion Error FAQ

How does Signed to Unsigned Conversion Error occur?

Signed to Unsigned Conversion Error occurs when a signed primitive is cast to an unsigned primitive, producing unexpected values if the value of the signed primitive can’t be represented using an unsigned primitive.

What are the common consequences of Signed to Unsigned Conversion Error?

The common consequences of Signed to Unsigned Conversion Error include Unexpected State and Integrity issues.

How do I detect Signed to Unsigned Conversion Error in my code?

You can use manual testing, automated scanners (SAST / DAST), or PenScan’s detection capabilities to identify Signed to Unsigned Conversion Error.

What are the framework-specific fixes for Signed to Unsigned Conversion Error?

The framework-specific fixes for Signed to Unsigned Conversion Error include using unsigned primitives in C and C++.

How do I prevent Signed to Unsigned Conversion Error in my code?

You can use unsigned primitives, validate input values, and check for overflow conditions to prevent Signed to Unsigned Conversion Error.

Can AI help me detect and fix Signed to Unsigned Conversion Error in my code?

Yes, you can use AI coding assistants to review your code for potential CWE-195 Signed to Unsigned Conversion Error vulnerabilities and rewrite it using primary fix techniques.

What are the best practices for preventing Signed to Unsigned Conversion Error?

The best practices for preventing Signed to Unsigned Conversion Error include using unsigned primitives, validating input values, checking for overflow conditions, and reviewing your code regularly.

How do I know if my code has Signed to Unsigned Conversion Error?

You can use manual testing, automated scanners (SAST / DAST), or PenScan’s detection capabilities to identify Signed to Unsigned Conversion Error in your code.

Vulnerabilities Related to Signed to Unsigned Conversion Error

References

• MITRE CWE-195
• 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 Signed to Unsigned Conversion Error and other risks before an attacker does.