Apple users know that one of the big reasons for sticking with iPhones, Macs, or even Apple Watches is the company’s longstanding reputation for strong security. But like all software, vulnerabilities crop up, and sometimes, the risks are bigger than they seem at first glance. CVE-2022-42795 is a perfect example: at first, it's just a “memory consumption issue.” But it’s a loophole that could have let a hacker run code on your device—just by convincing you to open a picture.
In this long read, we’ll break down what CVE-2022-42795 actually is, talk about how attackers could have used it, dive into official references, and explore the Apple patch that closed the door for good. You’ll also see some code snippets and quick, simple explanations—even if you don’t code. If you’ve ever wondered how “a bad image file” can threaten your phone or MacBook, this is the place to start.
What is CVE-2022-42795?
CVE-2022-42795 is a vulnerability related to how Apple devices handled certain image files in memory. According to Apple’s own security updates, this weakness affected:
watchOS 9
More specifically, it means that an attacker could create a malicious image file. If you opened the image on your Apple device, the way your device tried to process and show that image could cause a memory consumption issue—and in a worst-case scenario, allow the attacker to run their own code on your device. This is known as arbitrary code execution.
It doesn’t matter how you get the image: it could be a photo you received in a message, an image you downloaded from a website, or even a picture in an email.
Apple’s security advisory puts it simply
> “A memory consumption issue was addressed with improved memory handling. Processing a maliciously crafted image may lead to arbitrary code execution.”
> Apple Security Update — HT213488
How Did the Exploit Work?
Let’s break this down simply. Modern devices load images into memory to show them on screen. If the image “lies” about its size or tricks the device into using more memory than it should, this can lead to a crash or, worse, give hackers a way to sneak their code into that memory space.
The attacker’s code (hidden in the image) is placed in this memory and executed.
Engineers call this a heap overflow, where too much data spills out in places it shouldn’t go.
A Peek at the Technical Details
Let’s imagine a simplified version of vulnerable code handling image metadata. Note: This is NOT the actual Apple source, but it’s inspired by similar vulnerabilities in open source image libraries (for example, libjpeg or libpng):
Before (Vulnerable Code)
// Mockup: reading size from image header
int width = read_from_header(img_data, "width");
int height = read_from_header(img_data, "height");
char *buffer = malloc(width * height * 4); // Potentially huge!
// Later...
copy_image_data(buffer, img_data);
If an attacker puts huge fake numbers in the image’s header, width * height * 4 becomes enormous, and malloc might fail or allocate less memory than expected, or, worse, not check for integer overflows. If that happens, the next copy_image_data might overwrite important memory—segmenting a path for code execution.
After (Patched Code)
// Apple would check for reasonable image sizes
if (width < || width > MAX_WIDTH || height < || height > MAX_HEIGHT) {
return ERROR;
}
size_t bufsize = width * height * 4;
// Additional overflow check
if (bufsize / 4 != width * height) {
return ERROR; // Overflow detected!
}
char *buffer = malloc(bufsize);
if (!buffer) {
return ERROR;
}
copy_image_data(buffer, img_data);
In the updated code, bounds and overflows are checked, so malicious headers can’t request unreasonable memory or corrupt memory blocks.
What Could an Attacker Do?
If this sounds hard to pull off, you might be right—it’s not trivial. But it’s not science fiction, either. These kinds of vulnerabilities are regularly exploited at hacking competitions like Pwn2Own.
You open the image on an unpatched device.
- Hidden code in the image grants the hacker backdoor access or makes your device run crypto-mining code.
Apple patched this in their major Fall 2022 updates
- macOS 13 Ventura security content
- iOS 16 Security updates
- watchOS 9 release notes
- tvOS 16 update
They mention “improved memory handling,” which usually means tighter bounds checking and validating all image headers before committing any memory allocations.
Real-World Exploit Example
Because this vulnerability is now patched and wasn’t publicly weaponized widely, there’s no “click–to–get–pwned” real-world exploit you can easily copy and paste. However, security researchers often demonstrate similar issues with fuzzing tools that automatically generate weird, broken image files, then observe when the device glitches or leaks memory.
For example, to test a program for memory errors, you might use a tool like AFL fuzzer:
afl-fuzz -i input_images -o findings -- ./image_parser
If the image parser crashes or uses excessive memory, that’s a sign of a vulnerability.
If a proof-of-concept exploit were available, it might look like
# Skeleton for generating an exploit image (JUST AN EXAMPLE)
from PIL import Image
# Dominated by huge (fake) dimensions that cause memory allocation failure
img = Image.new('RGBA', (1_000_000, 1_000_000))
img.save('exploit.png')
Of course, real hackers add custom payloads and tricks specific to the vulnerable code path.
Protecting Yourself
Simple rule:
Update, update, update!
If your Apple device is running any of these operating systems, make sure you’re on the latest version. Apple is pretty aggressive about pushing updates for critical vulnerabilities, but don’t snooze on those pop-ups.
Pro tip:
If you use old devices that can’t run iOS 16 or macOS Ventura, think about restricting how you open files from unknown sources—especially images!
- Apple’s official update
- HT213488 — About the security content of macOS Ventura 13.
- HT213446 — iOS 16 security update notes
- General info for CVE-2022-42795
- Learn about fuzzing and memory issues
- Google Project Zero writeup on image parsing vulnerabilities
- The Art of Exploitation (PDF)
In Summary
CVE-2022-42795 is a reminder that even something as simple as an image file can be a backdoor into your most private devices, if the software behind it isn’t careful with memory. Apple’s fixes in late 2022 closed the hole, but only if you keep your devices updated.
Timeline
Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/02/2022 19:41:00 UTC