FortiDeceptor is a well-known deception-based security solution from Fortinet. But in 2022, a significant web application vulnerability was discovered that highlighted a weakness in how its management interface handled user input. In this detailed post, we’ll break down CVE-2022-38373, explain why it happens, walk you through how an attacker might exploit it, and offer resources for further reading. This article is written in clear, straightforward language for easier understanding.

What is CVE-2022-38373?

CVE-2022-38373 is a Cross-Site Scripting (XSS) security flaw found in certain versions of the FortiDeceptor management interface.

FortiDeceptor 4..2

What is the risk?
If someone with access to the interface sends specially crafted data (a "lure resource ID" containing malicious code), they could trick the system into running that code in another user’s browser. This is known as improper neutralization of input during web page generation (CWE-79).

Explaining XSS in Simple Terms

XSS (Cross-Site Scripting) happens when an application lets users send dangerous code (usually JavaScript) to other users without checking or cleaning it up first. If a user opens a page with this code, it runs in their browser as if it came from the trusted web app.

Where’s the Problem in FortiDeceptor?

The FortiDeceptor management interface had a loophole in how it displayed the "lure resource ID" on web pages. Instead of safely handling special characters, it would put whatever text was sent right into an HTML page. If that text was actually malicious JavaScript, it could be executed.

An attacker just needs to be authenticated (logged in). Unfortunately, in many environments, getting login details might not be very hard: neglected user accounts, weak passwords, or social engineering could all help.

Example Attack Scenario

Let’s suppose an attacker logs into FortiDeceptor and submits a specially crafted lure resource ID like this:

"><script>alert('XSS');</script>

If the application displays this ID directly in a web page without encoding it, the browser interprets <script>alert('XSS');</script> as real JavaScript. The victim’s browser will pop an alert box (or worse: run any code the attacker wants).

Code Snippet: Simulating the XSS Attack

Here’s a very simplified example of how the vulnerable behavior might look in Python Flask (for illustration only):

from flask import Flask, request, render_template_string

app = Flask(__name__)

@app.route('/lureinfo')
def lure_info():
    lure_id = request.args.get('id', '')
    # Vulnerable: directly inserts user input into HTML
    page = f'<html><body>Lure Resource ID: {lure_id}</body></html>'
    return render_template_string(page)

# Visiting /lureinfo?id=%22%3E%3Cscript%3Ealert('XSS')%3C%2Fscript%3E would trigger an alert in this example

What’s wrong here?
Input isn’t sanitized or “neutralized”—bad code gets into the page!

Proof-of-Concept Attack

To exploit, the attacker logs in and sends this HTTP request (for example, using Burp Suite, Postman, or a browser):

GET /lureinfo?id=%22%3E%3Cscript%3Ealert('XSS')%3C%2Fscript%3E HTTP/1.1
Host: fortideceptor.example.com
Cookie: session=VALID_SESSION_COOKIE

If another admin views the resource, their browser runs the <script>alert('XSS')</script>, showing an alert box. A real-world attack might steal their session cookie instead.

How to Prevent This

The correct way is to always encode or sanitize user-generated content before showing it in a web page. All major web frameworks have ways to do this, but this needs to be double-checked, especially with dynamic fields.

Official Fortinet advisory for CVE-2022-38373:

https://fortiguard.fortinet.com/psirt/FG-IR-22-212

National Vulnerability Database entry:

https://nvd.nist.gov/vuln/detail/CVE-2022-38373

Common Weakness Enumeration explanation for CWE-79:

https://cwe.mitre.org/data/definitions/79.html

Conclusion

CVE-2022-38373 is a reminder that even security products can have dangerous web application flaws. Cross-site scripting can lead to very bad consequences—but it’s also one of the easiest mistakes to fix if you follow secure coding practices. If you run FortiDeceptor, patch now and keep your users safe!


*This guide is written exclusively and does not copy from any existing articles. Please see the links above for original advisories and technical details about CVE-2022-38373.*

Timeline

Published on: 11/02/2022 12:15:00 UTC
Last modified on: 11/03/2022 13:51:00 UTC