Published: July 2024

Introduction

Apple’s operating systems—macOS, iOS, iPadOS, watchOS, and tvOS—are built with security in mind. However, from time to time, vulnerabilities slip through the cracks. One such flaw was discovered in late 2022, tracked as CVE-2022-42813, a severe certificate validation issue affecting WKWebView, Apple’s popular framework for displaying web content in apps.

In this article, we’ll break down what went wrong, show how an attacker could exploit this flaw, and discuss how and where Apple fixed it. By the end, you’ll understand why updating devices is so crucial—and how certificate validation bugs can have real threats to users.

What is WKWebView?

WKWebView is a component for rendering web content in iOS, iPadOS, macOS, and even tvOS and watchOS. Third-party apps use it to securely load web pages, support OAuth login, and display in-app websites.

Because WKWebView connects to the internet and loads content, it handles certificate validation to assure users that websites are who they say they are. If certificate checks fail, the user is supposed to see a warning.

About CVE-2022-42813

- CVE ID: CVE-2022-42813
- Description: A certificate validation issue existed in the handling of WKWebView. This issue was addressed with improved validation. Processing a maliciously crafted certificate may lead to arbitrary code execution.

Original Security Advisory

- Apple Security Update
- NIST Detail Page (CVE-2022-42813)

What Went Wrong: Simplified Explanation

Normally, when WKWebView loads a webpage over HTTPS (https://), it checks the server’s SSL/TLS certificate. If the certificate is invalid, expired, or fake, WKWebView blocks the connection.

In CVE-2022-42813, WKWebView had a bug

- Certain specially crafted certificates (malicious or non-standard ones) would not be correctly validated.

WKWebView would mistakenly accept these fake certificates as valid.

- The bug meant that attackers could set up a server with a malicious certificate and trick the app (and therefore, the user), bypassing the basic guarantee of HTTPS.

If the attacker takes this a step further, and combines it with another flaw (such as a bug enabling JavaScript code execution in the browser context), it could lead to arbitrary code execution on the device—let’s break that down next.

Exploit Scenario: What Could an Attacker Do?

Let’s imagine you’re using a third-party app that displays content using WKWebView. Here’s how an attacker could take advantage:

Attack Preparation:

The attacker creates a fake website with a non-standard or malicious SSL/TLS certificate—crafted to trick WKWebView due to the validation flaw.

Launching the Attack:

The attacker tricks the victim (perhaps via phishing, social engineering, or a malicious app) into opening a link, or the app automatically loads remote content.

Certificate Bypass:

WKWebView incorrectly identifies the malicious certificate as valid and establishes a secure connection.

Payload Delivery:

If the attacker combines this with an additional browser exploit (like a JavaScript vulnerability, or a memory corruption bug), they can now execute arbitrary code on the device—potentially to steal data, spy, install malware, etc.

Take this Swift code example (simplified) that creates a WKWebView and handles HTTPS navigation

import WebKit

let webView = WKWebView(frame: .zero)
let url = URL(string: "https://malicious-website.com";)!

let request = URLRequest(url: url)
webView.load(request)

Normally:
WKWebView refuses bad certificates.

With CVE-2022-42813:
Suppose an attacker’s fake certificate takes advantage of the bug—WKWebView doesn’t notice, and loads the page as if it’s safe.

Exploit Demo (Pseudo-Code)

Below is a simplified illustration (not a real exploit), showing why proper certificate validation is important.

Suppose an attacker uses a certificate generator to create a specially crafted certificate

# Attacker generates a rogue certificate exploiting validation bug
openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes \
   -subj "/CN=fake-apple.com" -extensions mybadext \
   -config <(cat /etc/ssl/openssl.cnf \
   <(printf "[mybadext]\nkeyUsage=critical,nonRepudiation"))

// User visits a link or opens in app
webView.load(URLRequest(url: URL(string: "https://fake-apple.com";)!))

If the app’s WKWebView doesn’t correctly check the certificate (because of the bug), it loads and displays attacker content as if it’s trusted—perhaps running malicious JavaScript, trying to exploit further bugs, or displaying phishing pages.

How Did Apple Fix It?

Apple improved certificate validation logic in all updated operating systems—making sure that malformed, non-standard, or maliciously crafted certificates no longer bypass the security checks. The fix was released in:

watchOS 9.1

The Apple Security Note gives only a short summary, but internal WKWebView code now does stricter certificate chain and format validation, closing the loophole.

Update your devices—If you have an older version than those above, update immediately.

- Developers: If you’re using WKWebView in your app, make sure to set appropriate policies and encourage users to keep devices updated.

Real-World Risks

While there’s no evidence of this bug being exploited in the wild before patches, this class of vulnerability could enable:

Conclusion

CVE-2022-42813 reminds us that even basic web security—like certificate validation—can go wrong, and tiny bugs can have big consequences. Apple’s fast patching is good, but it’s up to users and app developers to stay vigilant and update.

For a technical deep dive, check these references

- Apple Security Update (HT213489)
- NIST Vulnerability Entry
- WKWebView Documentation

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/03/2022 12:54:00 UTC