How to Find CSRF Vulnerabilities Using Kali Linux: A Full Methodology

Before diving into detection, let’s take a moment to understand how CSRF works. In essence, a CSRF attack involves exploiting a web application’s trust in a user’s browser. The attacker tricks an authenticated user into executing a malicious request, usually by embedding a crafted link or script into a web page, email, or message. Since the victim’s browser automatically includes authentication credentials (like cookies or session tokens) in the request, the server believes the request is legitimate.

CSRF vulnerabilities are common in:

Forms that submit sensitive data like password changes or financial transactions.Actions that rely on user session authentication, such as deleting accounts or modifying user settings.

The main indicators of a CSRF vulnerability are:

Missing anti-CSRF tokens in forms or URLs.The application relies solely on GET or POST methods without additional verification mechanisms.No referrer or origin checking to confirm that the request originates from a trusted source.

Kali Linux comes with a comprehensive suite of tools to help identify and exploit web vulnerabilities. For CSRF detection, we’ll use tools like Burp Suite, OWASP ZAP, and simple manual techniques.

Step 1: Reconnaissance

Before testing for CSRF, gather information about the target application. This includes:

Targeting User-Authentication Mechanisms: CSRF typically affects authenticated actions, so the first step is to gain access to the web application as a user. This could involve using credentials if available, or targeting login pages to attempt brute force or session fixation attacks.Identifying User-Accessible Functions: Focus on actions that modify sensitive data, such as changing user settings, making transactions, or deleting records. These actions are more likely to be vulnerable.

Tools for Reconnaissance:

Burp Suite: Use the “Spider” and “Scanner” tools to map out the application and identify all the endpoints.OWASP ZAP: Leverage the “Active Scan” feature to automatically detect potential CSRF vulnerabilities.Manual Browsing: Manually inspect URLs, forms, and requests in the browser to look for areas where sensitive actions are performed.

Step 2: Analyze Forms and Requests

After identifying potential attack surfaces, such as forms or actions that modify data, the next step is to inspect the requests these actions generate.

Inspect HTML Forms for Anti-CSRF Tokens:

Look for hidden input fields or headers that contain CSRF tokens. CSRF tokens should be unique per session or request to be effective.Example: <input type="hidden" name="csrf_token" value="unique_token_value">

Review HTTP Requests for Session Handling:

CSRF is only effective when the application relies on cookies or session tokens to authenticate users. Check if the application includes cookies like sessionid in the request headers or URLs.Tools like Burp Suite’s Proxy can help inspect HTTP traffic, showing the headers and body of requests.

Look for Actions Triggered by GET Requests:

GET requests should be used for fetching data, not modifying it. If actions like deleting an account or changing a password can be triggered via GET, this could be a CSRF vulnerability.

Step 3: Attempt Exploitation Using Burp Suite

Once you have a good understanding of the target, it’s time to test for CSRF vulnerabilities. One of the most efficient ways to test is by crafting malicious requests.

Set Up Burp Suite’s Proxy:

Start by configuring Burp Suite’s Proxy to intercept your requests and responses.Visit the target web application in your browser and use Burp Suite to capture the HTTP request when performing actions like changing account settings or submitting forms.

Replay the Request with Modified Parameters:

Modify the captured request to simulate a CSRF attack. For example, change the target URL, form parameters, or session cookie values.Craft a malicious URL or HTML page that submits this request on behalf of the victim. For example:

<img src=”https://example.com/account/delete?user_id=12345" style=”display:none;”>

Automate CSRF Detection with Burp Suite:

Burp Suite Pro offers a Scanner that can automatically detect CSRF vulnerabilities. It scans common requests, checking for missing anti-CSRF tokens and unsafe HTTP methods.

Step 4: Validate with Manual Testing

While automated tools are helpful, manual validation is crucial to verify the effectiveness of CSRF attacks:

Test the Application’s Response:

If the attack succeeds, the web application will perform the sensitive action without the user’s knowledge. You can test this by sending the malicious request to a victim (or yourself in a test environment) and checking if the action occurs.

Check for Token Validation:

If anti-CSRF tokens are implemented, try removing them or changing their values. If the application fails to validate the token correctly, it’s potentially vulnerable.

Step 5: Reporting Vulnerabilities

Once you’ve identified a CSRF vulnerability, document your findings clearly and responsibly. Include:

The exact location of the vulnerable functionality (URLs, form names).Steps to reproduce the attack, including any modifications made to the request.Recommendations for mitigating CSRF, such as implementing anti-CSRF tokens, checking the Origin or Referer headers, and using SameSite cookies.

To fix CSRF vulnerabilities, developers should adopt the following measures:

Implement Anti-CSRF Tokens: These should be included in all state-changing requests and validated by the server.Use SameSite Cookies: Configure cookies with the SameSite attribute to limit cross-site requests.Check Origin/Referer Headers: Ensure that requests are coming from trusted sources.Limit GET Requests for Sensitive Actions: Use POST requests for actions that modify data, and ensure they are protected by CSRF tokens.