Summary:
In late 2022, Apple patched a critical kernel vulnerability known as CVE-2022-42801. This bug affected devices running iOS, iPadOS, macOS, tvOS, and watchOS, allowing a malicious app to execute arbitrary code with kernel privileges – essentially full control over the device. In this post, we’ll walk through how the bug works, how it can be exploited, and review the fix, using code snippets and practical examples to help you understand the risk.

watchOS (before 9.1)

- Impact: Malicious app can execute code as the *kernel* (root of the system), bypassing security protections.

Original References:
- Apple Security Updates, Nov 2022
- NIST NVD Entry

Technical Details

The core of CVE-2022-42801 is a logic issue during kernel privilege checks. The Apple kernel includes subsystems where user-space (apps) can interact with kernel code for services like graphics, networking, or drivers. To prevent abuse, the kernel enforces validations before performing dangerous operations.

In this case, due to a flawed check, a malicious app could trick the kernel into executing code via a crafted object, allowing privilege escalation.

How the Bug Works

*Note: Apple deliberately avoids giving detailed exploitation steps in advisories. What follows is a simplified, hypothetical scenario based on public reports and typical Apple kernel vulnerabilities.*

A user app submits data or requests (via syscall or XPC to kernel extension).

2. Kernel code validates the data structure, but due to a logic issue, certain invalid objects or pointers are not correctly blocked.
3. Attacker introduces crafted data that leads the kernel to misinterpret or dereference a pointer—either causing a write-what-where or allowing arbitrary code execution.

Exploit Walkthrough (Simplified Example)

Here is pseudocode that shows where such logic issues can happen. Suppose a kernel API is expected to check a struct provided by user apps:

typedef struct {
    uint32_t length;
    char *data;
} user_input_t;

// Vulnerable kernel code
int process_input(user_input_t *input) {
    // Logic issue: doesn't check 'input->length' against safe max
    char buffer[256];
    memcpy(buffer, input->data, input->length); // Unsafe: buffer overflow if length > 256
    // ... (do more with buffer)
    return ;
}

Real Example

Public exploit codes for Apple kernel flaws are rare and dangerous, but the general steps for exploiting such bugs are:

1. Find an interface/exported API where you can send untrusted data to the kernel

Use the kernel’s own processing of your data to execute code of your choice

*This is a hypothetical code path. The real CVE-2022-42801 may differ, but follows similar privilege escalation techniques.*

Real-World Impact

- Jailbreaking: Such bugs can be weaponized to bypass iOS's security features and enable jailbreaking, as has historically happened with kernel issues.
- Attack Chain: Combined with a Safari/WebKit bug, an attacker could remotely compromise a device – web page launches code, code escapes sandbox, kernel bug gives full root.
- Enterprise Espionage & Targeted Attacks: These exploits are highly sought after by APTs and spyware vendors (e.g., Pegasus).

The Fix: Improved Checks

According to Apple, the fix for CVE-2022-42801 was "addressed with improved checks." That usually means:

Key Takeaways

- CVE-2022-42801 is a kernel privilege escalation bug impacting nearly all current Apple platforms.

Allows any app – even from the App Store – to get unrestricted device access.

- Exploiting this vulnerability requires a crafted payload, taking advantage of a logic flaw in kernel input validation.

Learn More

- Apple HT213489: About the Security Content of iOS 16.1 and iPadOS 16
- NIST NVD CVE-2022-42801
- Kernel Exploitation Basics *(External reference)*

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Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/03/2022 03:53:00 UTC