In May 2022, Apple addressed a significant security vulnerability identified as CVE-2022-26763, which affected several of its operating systems including iOS, iPadOS, macOS, tvOS, and watchOS. This vulnerability stemmed from an out-of-bounds access issue, potentially allowing malicious apps to execute arbitrary code with system privileges—a serious risk.

This article breaks down CVE-2022-26763 in easy-to-understand language, provides links to Apple’s original advisories, highlights the impact, and demonstrates how such a vulnerability can be exploited with exclusive code snippets.

What is CVE-2022-26763?

CVE-2022-26763 is an out-of-bounds access vulnerability. In programming, “out-of-bounds” occurs when software tries to read or write data past the end (or before the start) of a memory buffer. If this happens, it can corrupt data, crash the application, or, in worse cases, allow an attacker to run malicious code with high privileges.

> Apple’s summary:  
> “An out-of-bounds access issue was addressed with improved bounds checking. A malicious application may be able to execute arbitrary code with system privileges.”

Security Update 2022-004 Catalina

If you use any of these systems, you should make sure they are up-to-date.

Vulnerable Code Pattern

The issue was resolved by adding better bounds checking. Here’s a general pattern of how out-of-bounds access can happen in C/C++ code:

void processInput(int *input, size_t len) {
    int buffer[10];
    for (size_t i = ; i < len; i++) {
        buffer[i] = input[i]; // Vulnerability: What if len > 10?
    }
}


If len is greater than 10, the loop writes *past the end* of the buffer.

Unsafe Behavior

A malicious actor could craft input that causes the loop to overwrite memory outside buffer. That overwritten memory might contain code pointers, security flags, or other structures, letting the attacker hijack program flow.

Here’s a simple (theoretical) exploit snippet in pseudocode

int malicious_input[20];
// Fill malicious_input with data so that buffer[10..19] overwrites critical memory
fill_input(malicious_input);
processInput(malicious_input, 20);
// Now, if system calls a function pointer that lives after buffer, attacker gains exec

Note: Real-world attacks are more complex and depend on the exact arrangement of memory and system protections like DEP and ASLR, but this is the underlying concept.

How Apple Fixed It

Apple fixed the vulnerability by improving bounds checking. The improved code now properly ensures a buffer isn’t overrun:

void processInput(int *input, size_t len) {
    int buffer[10];
    size_t safe_len = len < 10 ? len : 10;
    for (size_t i = ; i < safe_len; i++) {
        buffer[i] = input[i]; // Safe: No out-of-bounds
    }
}

Original References

- Apple Security Updates: iOS 15.5 and iPadOS 15.5
- Apple Security Updates: macOS
- NVD Details: CVE-2022-26763
- Apple Security Updates: watchOS 8.6

Takeaways

CVE-2022-26763 was a subtle but significant vulnerability—demonstrating how a single unchecked boundary can lead to device compromise. Even the world’s most secure devices can be at risk from such coding bugs.

Quick Q&A

Q: Can this be exploited remotely?  
A: No, an attacker must get the user to install a malicious app first.

Q: What kind of apps can exploit this?  
A: Any app with access to the affected APIs could potentially exploit the flaw if unpatched.

Conclusion

CVE-2022-26763 is a good reminder of how crucial secure coding practices are, especially in low-level system work. Thanks to prompt Apple updates, risks have been mitigated—but the lesson in checking array bounds is one we should all remember.


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*References:*
- Apple Security Advisory for iOS 15.5 – HT213255
- CVE Details – NIST NVD

Timeline

Published on: 05/26/2022 20:15:00 UTC
Last modified on: 06/08/2022 12:49:00 UTC