CVE-2023-47845: Cross-Site Request Forgery (CSRF) vulnerability in Lim Kai Yang's Grab & Save affecting versions up to 1..4

Introduction:
A recent vulnerability has been discovered in Lim Kai Yang's Grab & Save. This post will provide an in-depth analysis of the Cross-Site Request Forgery (CSRF) issue (CVE-2023-47845), which affects Grab & Save versions from n/a up to 1..4. We will detail the exploit, the affected code, and some potential solutions to mitigate this security risk.

Summary:
CVE-2023-47845 represents a CSRF vulnerability in Grab & Save, which is a popular file transfer application. In a CSRF attack, an attacker can trick the victims into performing unwanted actions on the target web application without their consent, simply by sending them a specially crafted link. This vulnerability can lead to severe security risks, such as unauthorized access and data theft.

Exploit Details:
The vulnerability lies in the web application's lack of checking for valid anti-CSRF tokens and not having proper user authentication. Consequently, an attacker can craft a malicious link that, when visited by an authorized user, will execute unwanted actions in the context of the victim's account.

For example, an attacker can craft a URL similar to the following

http://example.com/grabandsave?action=delete&file=important_document.pdf

If the victim clicks on the link, the "important_document.pdf" file will be deleted without their consent due to the CSRF vulnerability.

Here is an example of a vulnerable code snippet in the application

@app.route('/grabandsave', methods=['POST'])
def grab_and_save():
    action = request.form.get('action')
    file_name = request.form.get('file')

    if action == 'delete':
        delete_file(file_name)
        return "File deleted successfully", 200
    else:
        return "Invalid action", 400

As seen above, the web application does not check for valid anti-CSRF tokens or perform any user authentication, thus leaving the application exposed to CSRF attacks.

To fix this vulnerability, developers should perform the following steps

1. Implement proper user authentication by implementing secure login mechanisms such as access tokens or OAuth.

2. Generate and validate anti-CSRF tokens for each session, then include them in each request header or form data. For example, you can use the "csrf_token" feature provided by the Flask web framework:

from flask_wtf import CSRFProtect

...

csrf = CSRFProtect(app)

...

@app.route('/grabandsave', methods=['POST'])
@csrf.protect()
def grab_and_save():
    ...

3. Ensure that cookies used for session management are set with secure flags such as "HttpOnly" and "Secure."

For more information about this vulnerability and its mitigation, you can visit the following links

1. NIST National Vulnerability Database (NVD) - CVE-2023-47845
2. OWASP Cheat Sheet on CSRF - Cross-Site Request Forgery (CSRF) Prevention Cheat Sheet

Conclusion

In conclusion, the Cross-Site Request Forgery (CSRF) vulnerability in Lim Kai Yang's Grab & Save (CVE-2023-47845) poses a significant security risk to users who are running affected versions (from n/a through 1..4). By implementing proper user authentication, anti-CSRF tokens, secure cookie flags, and Content Security Policy, developers and users alike can effectively mitigate this vulnerability and protect their web applications from potential attacks.

Timeline

Published on: 06/12/2024 10:15:27 UTC
Last modified on: 06/13/2024 18:36:09 UTC