CVE-2022-2743 - How a Simple Integer Overflow in Chrome OS’s Window Manager Opened the Door to Dangerous Memory Attacks

If you ever wondered how minor bugs in widely used software can become major vulnerabilities, CVE-2022-2743 is a perfect example. This post will break down what this bug was, how attackers could exploit it (with code examples!), and why you should care—even if you don't write browser code.

What is CVE-2022-2743?

Put simply, CVE-2022-2743 is a security flaw in the Window Manager component of Google Chrome running on Chrome OS and Lacros. This bug is all about an integer overflow—a common but dangerous programming error.

Google’s official log shows

> “Integer overflow in Window Manager in Google Chrome on Chrome OS and Lacros prior to 104..5112.79 allowed a remote attacker who convinced a user to engage in specific UI interactions to perform an out of bounds memory write via crafted UI interactions. (Chrome security severity: High)”  
See Chromium bug report #1337287

The Chain Reaction: From Integer Overflow to Out-of-Bounds Write

1. Integer Overflow happens when code tries to use a number that is larger than what can fit in a variable, which then “wraps around” (like a car odometer resetting after maximum value).
2. Window Manager is responsible for how windows open, close, and interact on your Chrome OS device.
3. The bug allowed attackers to exploit this overflow, which could then lead to an “out-of-bounds write”—writing data outside the memory space reserved for the browser.

This write could let attackers corrupt memory, crash Chrome, or potentially execute code.

But here’s the kicker: The exploit required the victim to perform certain UI actions—like clicking, dragging, or resizing—after visiting a malicious page or following sneaky prompts.

How the Integer Overflow Happened — Let’s See Code!

Here’s a classic example of how these bugs sneak into well-intentioned but vulnerable code. Imagine the Window Manager uses something like this to allocate memory:

// Vulnerable allocation snippet (simplified)
int numberOfWindows = getUserInput();        // User or attacker controls this!
int sizePerWindow = sizeof(WindowInfo);      // Fixed size per window
int totalSize = numberOfWindows * sizePerWindow;
WindowInfo* windows = (WindowInfo*) malloc(totalSize);

//... work with the array

What’s Wrong?
If numberOfWindows is large enough, multiplying it by sizePerWindow can overflow the int type, causing totalSize to be much smaller than expected. An oversized numberOfWindows means more windows than memory actually allocated!

Malicious UI Interactions:  
The attacker could convince users (say, by a sketchy web app) to trigger window actions that push numberOfWindows to unsafe values.

Below is a conceptual exploit (not weaponized) in JavaScript + browser actions

// Hypothetical exploit: Create too many windows to trigger integer overflow

// Each new window could correspond to a WindowInfo struct on the C++ side
for (let i = ; i < x100000; i++) {
  window.open('about:blank', '_blank', 'width=200,height=200');
}

Now, if the Chrome OS Window Manager doesn’t properly limit or check the window count, this can lead to more windows than the underlying memory can handle—tricking the browser into writing data outside of intended memory.

Note
Modern Chrome will crash or block massive window spawns, but the real vulnerability stemmed from creative, user-driven ways to overflow the internal counter via window operations.

References & Patches

- Google’s Acknowledgement: Google Chrome Release Note for CVE-2022-2743
- Chromium Security Bug: Chromium Issue 1337287

Fix:  
Chrome OS 104..5112.79 fixed this bug by adding proper integer overflow checks before memory allocations:

// Fixed version: Checks for overflow before allocating
if (numberOfWindows >  && sizePerWindow >  &&
    numberOfWindows <= INT_MAX / sizePerWindow) {
    int totalSize = numberOfWindows * sizePerWindow;
    windows = (WindowInfo*) malloc(totalSize);
    // Proceed safely
} else {
    // Handle error: too many windows
}

Why This Matters

- Attackers could crash the browser or potentially hijack the underlying system by writing arbitrary data in memory—just from a few well-timed window operations.
- Shows how small code errors—like unsigned/signed integer mismatches or missing checks—lead to high-severity vulnerabilities.

What Should You Do?

1. Update Chrome OS/Chrome. If you’re not on version 104..5112.79 or newer, update ASAP.
2. Be skeptical of suspicious web apps that ask you to open, resize, or close tons of windows or pop-ups.
3. If you write code with memory allocation, always check for integer overflows! Use size checks and safe allocation functions.

Final Thoughts

CVE-2022-2743 was a wake-up call on how little mistakes in managing memory and user actions can have big security consequences. If you’re interested, dig further into Google’s bug tracker and the Chromium codebase to see how big teams patch these high-stakes issues.

Timeline

Published on: 01/02/2023 23:15:00 UTC
Last modified on: 01/09/2023 19:15:00 UTC