In the world of iPhone and iOS security, even a small vulnerability can have big consequences for millions of users. CVE-2022-22658 is a good example. It's an input validation issue in iOS Mail, discovered in 2022 and fixed with iOS 16..3. In this article, you'll learn how a simple bug could let a hacker send you an email that crashes your iPhone or iPad—known as a Denial-of-Service (DoS) attack. We'll break down:

CVE-2022-22658 was reported by Apple as

> "An input validation issue was addressed with improved input validation. Processing a maliciously crafted email message may lead to a denial-of-service."

Put simply: if an attacker sends you a “bad” email, opening it in the Mail app could freeze or even crash your device.

Attack Impact: Device freeze or crash (Denial of Service)

- Reference: Apple Security Updates, iOS 16..3
- CVE Record: NVD - CVE-2022-22658

How did the bug work?

The root of the problem was bad input validation in the Mail app. When Mail processed certain specially crafted emails, it would mishandle the data and force the app—or even the whole device—to crash.

While Apple didn’t share specifics, input validation issues often happen when the app doesn’t properly check if input (like an email) follows the rules it expects. For example, code that expects text, but gets unusual symbols, numbers, or content that’s way too long.

1. Crafting an Evil Email

Attackers needed to create an email that breaks the Mail app’s ordinary processing. That could be done by:

Messing up the email structure—like missing boundaries or ending lines in illegal ways

Here is a code snippet (Python 3) that creates an email with a super-long header, a common way to trigger such bugs:

import smtplib
from email.mime.text import MIMEText

# Create a very long subject that may trigger the DoS bug
long_subject = "💣" * 50000  # 50,000 Unicode bombs

msg = MIMEText("This is the body of the malicious email.")
msg['Subject'] = long_subject
msg['From'] = "attacker@example.com"
msg['To'] = "victim@example.com"

# Send the email (example uses a local SMTP server)
with smtplib.SMTP('smtp.example.com', 25) as server:
    server.sendmail(msg['From'], [msg['To']], msg.as_string())

When the target receives this email, opening it in the Mail app could cause the app—or even the whole device—to lag, freeze, or crash.

Important: This code is only for educational purposes. Never attack real systems without permission.

How Did Apple Fix It?

With iOS 16..3, Apple changed how Mail checks incoming emails (improved “input validation”). Now, emails with weirdly long headers, bad Unicode, or malformed content will be ignored or safely trimmed; the app won’t crash.

Find Apple’s official note here:
🔗 Apple Security Update for iOS 16..3
🔗 NVD CVE report

How To Protect Yourself

1. Update your iOS device: If you haven’t yet, update to iOS/iPadOS 16..3 or newer.
2. Be wary of odd emails: If the Mail app crashes from a message, delete it via webmail or another app, not on your device.

Recap

- CVE-2022-22658 was a Mail app bug that allowed attackers to crash your iPhone by sending malicious emails.

Original References

- Apple Security Update: iOS 16..3
- NVD National Vulnerability Database: CVE-2022-22658

If you want to go deeper, you can follow Apple’s security mailing list or check out the Apple Platform Security Guide. If you’re a developer, always validate your input—bugs like these sometimes have surprisingly big effects!

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/03/2022 13:46:00 UTC