Apple’s devices are known for their robust security, but every now and then, a critical flaw surfaces, catching even the most diligent users off guard. In early 2022, a vulnerability catalogued as CVE-2022-22635 made headlines. This out-of-bounds write issue, affecting iOS, iPadOS, and tvOS, could allow a malicious application to gain elevated privileges—potentially granting root code execution. Let’s break down what happened, peek under the hood, and why you must keep your Apple devices updated.

What is CVE-2022-22635?

This vulnerability is an out-of-bounds write in the kernel component of iOS, iPadOS, and tvOS. Out-of-bounds write means an attacker can cause the system to write data outside the bounds of an allocated memory buffer. If exploited, this could result in corruption of critical data, privilege escalation, and arbitrary code execution with higher privileges.

Official Description

> "An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in tvOS 15.4, iOS 15.4 and iPadOS 15.4. An application may be able to gain elevated privileges."  
> *— Apple Security Updates*

Vulnerability Details

Before the patch, a weakness in how Apple’s system handled certain memory allocations meant a crafty application could “write” data past the end of a buffer. Without strict bounds checking, this could corrupt adjacent memory structures—often including process control structures or sensitive data.

The vulnerable function (example pseudocode, simplified)

int vulnerable_function(char *user_data, int user_size) {
    char buffer[100];
    // Inadequate bounds check!
    memcpy(buffer, user_data, user_size);
    // ...
    return ;
}


If the supplied user_size is greater than 100, memory just past buffer gets overwritten.

Exploit Details

While Apple has kept specific exploit details quiet (for obvious reasons), security researchers can extrapolate how such bugs are typically weaponized.

> Example Exploitation Steps:
> 1. The attacker creates a crafted application with code targeting the out-of-bounds write.
> 2. Malicious data is sent to the vulnerable function, overflowing the buffer.
> 3. Control structures after the buffer are overwritten—like a return address or a process privilege bitmask.
> 4. The attacker leverages the overwritten data to escalate their process privileges.

Here’s a simplified snippet to demonstrate the exploitation concept

// Malicious input triggers the bug
// Normally userData should not exceed 100 bytes
NSData *maliciousData = [NSMutableData dataWithLength:200];
sendToVulnerableFunction(maliciousData);

A real exploit would carefully calculate *what* to overwrite (e.g., pointers, permission flags) and *how*. On iOS and tvOS, such attacks often lead to sandbox escape or root-level code execution.

Patch & Mitigation

Apple fixed this in March 2022 via iOS, iPadOS, and tvOS version 15.4 with a simple, time-tested change: improved bounds checking.

Updated pseudocode for the fix

int secure_function(char *user_data, int user_size) {
    char buffer[100];
    // Proper bounds check!
    if (user_size > sizeof(buffer)) {
        return -1; // Reject!
    }
    memcpy(buffer, user_data, user_size);
    return ;
}

References & Further Reading

- Apple Security Advisory for iOS 15.4
- NIST CVE-2022-22635 Record
- About Out-of-Bounds Write Vulnerabilities

In Summary

CVE-2022-22635 showcases how a simple programming oversight can open the door to privilege escalation attacks—even on devices as locked-down as iPhones and Apple TVs. With the fix being a single update away, make sure all your devices are running the latest OS.

Stay safe by keeping your systems updated, and remember—bounds checking saves lives (and devices).

*Content exclusive to your request. If you have technical questions about CVE-2022-22635 or want to know more effects, drop a comment or reach out!*

Timeline

Published on: 03/18/2022 18:15:00 UTC
Last modified on: 03/24/2022 17:35:00 UTC