What is Download of Code Without Integrity Check (CWE-494)?

AI-friendly summary

What it is: Download of Code Without Integrity Check (CWE-494) is a type of software vulnerability that occurs when an application downloads and executes code without verifying its authenticity.

Why it matters: This can lead to unauthorized execution of commands, alteration of program logic, and potential compromise of system integrity and availability.

How to fix it: Implement cryptographic signatures and integrity checks before executing any remotely obtained code.

TL;DR: Download of Code Without Integrity Check (CWE-494) is a vulnerability where an application downloads and executes unverified code, leading to potential security breaches. Ensure proper verification mechanisms are in place.

Field	Value
CWE ID	CWE-494
OWASP Category	A08:2025 - Software or Data Integrity Failures
CAPEC	184, 185, 186, 187, 533, 538, 657, 662, 691, 692, 693, 695
Typical Severity	Medium
Affected Technologies	web applications, remote code execution
Detection Difficulty	Moderate
Last Updated	2026-07-29

What is Download of Code Without Integrity Check?

Download of Code Without Integrity Check (CWE-494) is a type of software vulnerability where an application downloads and executes source code or executable files from a remote location without verifying the origin and integrity of the downloaded content. This can lead to unauthorized execution of commands, alteration of program logic, and potential compromise of system integrity and availability.

As defined by the MITRE Corporation under CWE-494, and classified by the OWASP Foundation under A08:2025 - Software or Data Integrity Failures, this weakness is critical for web applications that rely on remote code execution without proper verification mechanisms in place.

Quick Summary

Download of Code Without Integrity Check occurs when an application downloads executable files or source code from a remote location and executes it without verifying its authenticity. This can lead to unauthorized command execution, alteration of program logic, and potential compromise of system integrity and availability. Proper verification mechanisms must be implemented before executing any remotely obtained code.

Download of Code Without Integrity Check Overview

What

Download of Code Without Integrity Check is a vulnerability where an application downloads and executes code without verifying its authenticity.

Why it matters

This can lead to unauthorized execution of commands, alteration of program logic, and potential compromise of system integrity and availability.

Where it occurs

Web applications that download and execute remote code without proper verification mechanisms are vulnerable.

Who is affected

Developers and organizations using web applications with the ability to download and execute unverified code.

Who is NOT affected

Applications that do not allow downloading or executing remotely obtained code.

How Download of Code Without Integrity Check Works

Root Cause

The root cause lies in the lack of proper verification mechanisms for downloaded code, allowing unauthorized execution of commands and potential compromise of system integrity and availability.

Attack Flow

An attacker identifies a vulnerable application that downloads and executes remote code without verifying its authenticity.
The attacker crafts malicious code to be downloaded by the application.
The application downloads and executes the malicious code, leading to unauthorized command execution and potential system compromise.
Prerequisites to Exploit
- Access to a vulnerable web application.
- Ability to influence the source from which code is downloaded.
  Vulnerable Code
  
```python import urllib.request

def download_and_execute(url): response = urllib.request.urlopen(url) code = response.read() exec(code) # Vulnerable: No integrity check before execution

This code downloads and executes remote code without verifying its authenticity, making it vulnerable to Download of Code Without Integrity Check.
### Secure Code
```python
import urllib.request

def download_and_execute_securely(url):
    import hashlib
    response = urllib.request.urlopen(url)
    code = response.read()
    
    # Verify the integrity of the downloaded code using a cryptographic hash
    if hashlib.sha256(code).hexdigest() == 'expected_hash':
        exec(code)  # Secure: Integrity check before execution

This secure version verifies the integrity of the downloaded code using a cryptographic hash before executing it, preventing unauthorized command execution.

Business Impact of Download of Code Without Integrity Check

Confidentiality

Exposure of sensitive data and access to restricted resources.
Integrity
Alteration of program logic leading to unexpected behavior.
Availability
Disruption of services due to malicious code execution. Business Consequences:
Financial losses from downtime or data breaches.
Reputational damage due to compromised systems.

Download of Code Without Integrity Check Attack Scenario

An attacker identifies a web application that downloads and executes remote code without proper verification mechanisms.
The attacker crafts malicious code designed to exploit the lack of integrity checks.
The attacker triggers the download mechanism, causing the application to execute the malicious code.
The malicious code gains unauthorized access to system resources and disrupts normal operations.

How to Detect Download of Code Without Integrity Check

Manual Testing

Review source code for instances where remote code execution occurs without proper verification mechanisms in place.
Verify that downloaded files are checked for integrity before being executed.
Automated Scanners (SAST / DAST)
Static analysis can detect the absence of integrity checks in code download functions.
Dynamic testing requires running the application to observe actual behavior during runtime.
PenScan Detection

PenScan’s scanner engines such as ZAP, Nuclei, Wapiti, Nikto, SSLyze, Dalfox, and Nmap are capable of identifying Download of Code Without Integrity Check vulnerabilities in web applications.

False Positive Guidance

False positives may occur if the code appears to be downloading remote files but is actually performing a benign operation. Ensure that any detected pattern is indeed part of an insecure download mechanism.

How to Fix Download of Code Without Integrity Check

Perform proper forward and reverse DNS lookups to detect DNS spoofing.
Encrypt the downloaded code with a reliable encryption scheme before transmitting it.
Use vetted libraries or frameworks that enforce proper verification mechanisms for remote code execution.
Run downloaded code in a sandbox environment with strict boundaries.

Framework-Specific Fixes for Download of Code Without Integrity Check

Python/Django

import urllib.request

def download_and_execute_securely(url):
    import hashlib
    response = urllib.request.urlopen(url)
    code = response.read()
    
    # Verify the integrity of the downloaded code using a cryptographic hash
    if hashlib.sha256(code).hexdigest() == 'expected_hash':
        exec(code)  # Secure: Integrity check before execution

This secure version verifies the integrity of the downloaded code using a cryptographic hash before executing it, preventing unauthorized command execution.

How to Ask AI to Check Your Code for Download of Code Without Integrity Check

Review the following Python code block for potential CWE-494 Download of Code Without Integrity Check vulnerabilities and rewrite it using proper verification mechanisms:

import urllib.request

def download_and_execute(url):
    response = urllib.request.urlopen(url)
    code = response.read()
    exec(code)  # Vulnerable: No integrity check before execution

Download of Code Without Integrity Check Best Practices Checklist

✅ Perform forward and reverse DNS lookups to detect DNS spoofing.
✅ Encrypt the downloaded code with a reliable encryption scheme before transmitting it.
✅ Use vetted libraries or frameworks that enforce proper verification mechanisms for remote code execution.
✅ Run downloaded code in a sandbox environment with strict boundaries.

Download of Code Without Integrity Check FAQ

How does Download of Code Without Integrity Check work?

It occurs when a web application downloads code from an untrusted source without verifying its authenticity, allowing malicious code to execute.

What are the common consequences of Download of Code Without Integrity Check?

This weakness can lead to unauthorized execution of commands and alteration of program logic, compromising system integrity and availability.

How do I detect Download of Code Without Integrity Check in my application?

Use PenScan’s automated scanners to identify instances where code is downloaded without proper verification mechanisms in place.

What are the best practices for preventing Download of Code Without Integrity Check?

Implement cryptographic signatures and integrity checks before executing any remotely obtained code to ensure its authenticity.

How can I fix Download of Code Without Integrity Check in my existing codebase?

Integrate secure libraries or frameworks that enforce proper verification mechanisms, such as Authenticode for signed executables.

What are the prerequisites for exploiting Download of Code Without Integrity Check?

The attacker must have access to a vulnerable application and be able to influence the source from which code is downloaded.

How can I manually test my application for Download of Code Without Integrity Check vulnerabilities?

Review your codebase for any instances where remote code execution occurs without proper integrity checks.

| CWE | Name | Relationship | |—|—|—| | CWE-345 | Insufficient Verification of Data Authenticity (ChildOf) | ChildOf | | CWE-669 | Incorrect Resource Transfer Between Spheres (ChildOf) | ChildOf |

References

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 Download of Code Without Integrity Check and other risks before an attacker does.