In mid-2022, Google publicly disclosed CVE-2022-1858, a vulnerability affecting Google Chrome’s DevTools. Before version 102..5005.61, a remote attacker could trigger an out-of-bounds memory read with a carefully crafted sequence of events that required specific actions from a user. If you're curious how this issue works, or what an “out-of-bounds” read in DevTools really means, let’s break it down step by step, with simplified code samples, real references, and an exclusive close-up on the exploit.

What is an Out-of-Bounds Read?

When a program tries to read (or access) memory outside the limits of what’s allowed for a given object, it’s doing an “out-of-bounds read.” These errors can leak sensitive data or crash the program.

In Chrome, most of these bugs are stopped by sandboxing and strict memory protections. But when they show up in components like DevTools, and they can be triggered remotely by web content, they become much more dangerous.

How Did CVE-2022-1858 Happen?

The root of this vulnerability was in how Chrome DevTools handled certain objects from web pages. DevTools tries to work with a lot of internal browser objects—sometimes ones influenced by the current page.

Before Chrome 102..5005.61, there was a code path where it was possible for crafted HTML/JS content to confuse DevTools into reading memory just outside the limits of an internal buffer. This required:

The attacker’s webpage having specific object structures.

3. Interaction by the user, like inspecting an element or running certain snippets in the DevTools console.

Example Vulnerable Code Path (Simplified)

Suppose DevTools has code like this (original code is C++, but let’s make an easy-to-read JavaScript simulation):

let buffer = [10, 20, 30, 40]; // Internal DevTools buffer

// Attacker finds a way to cause index to be out of range, say, 5
let index = 5; // Valid indices are -3

let value = buffer[index]; // Out-of-bounds! value = undefined or unexpected memory

In reality, DevTools was working with C++ objects, but the idea is the same: improper checks allow reading past the valid memory. In Chrome, reading a bad memory location doesn’t crash (thanks to protections)—instead, you might get garbage or, occasionally, leftover information from another process.

Lure the victim to a webpage you control.

2. Encourage them to open DevTools. You could do this with instructions, an interactive demo, or by triggering an error that prompts them.
3. Use crafted JavaScript/DOM structures so that, when an element is inspected (or a script is run in the console), DevTools triggers the bug.
4. Using the out-of-bounds read, leak information or potentially cause DevTools to reveal memory it shouldn’t.

PoC Code (Pseudo)

Real-world weaponization is complicated and ethically we’ll avoid giving working exploits. But for demonstration, an attacker could create a DOM structure designed to confuse DevTools:

// On attacker.com:
for (let i = ; i < 10000; i++) {
    let el = document.createElement('div');
    el.dataset.special = 'A'.repeat(100);
    document.body.appendChild(el);
}

// Instructions pop up:
// "Open DevTools, select the last div in Elements, then run inspect($)"

setTimeout(() => {
    // If DevTools inspects $ (last div), 
    // a specially crafted function could be triggered
}, 100);

Combined with browser quirks, the internal buffer bounds could get confused.

Real-World Impact

Unlike typical bugs, this one needed the victim’s help. But that doesn’t mean it wasn’t serious:

- Any public shared workspace: Someone could put malicious code on a dashboard; if another dev inspects it with DevTools, data leakage could occur.
- Customer support and QA scenarios: Frequently, users debug issues from untrusted sites with DevTools.

The Fix

Google patched this in Chrome 102..5005.61 by adding stricter bounds checking to the relevant code in DevTools. Here’s what a defensive fix would look like in code:

if (index >=  && index < buffer.size()) {
    value = buffer[index];
} else {
    // Log error, do not read memory!
}

Or in JavaScript

if (index >=  && index < buffer.length) {
    value = buffer[index];
} else {
    // Safe handling
}

References

- CVE-2022-1858 NVD Summary
- Chrome Stable Update 102..5005.61
- Chromium Security Bug Tracker Issue 1321425 (private) *(if request access is granted)*
- DevTools Security Docs

Conclusion

CVE-2022-1858 stands as an important reminder: even tools meant for power users, like DevTools, can hide vulnerabilities that attackers can exploit if the wrong piece falls into place. If you ever debug pages from the wider web, update your browser regularly—even DevTools isn’t immune.

If your work or habits take you into DevTools on untrusted sites, always stay on the lookout for updates, and follow Google’s security advisories. The browser security landscape is always evolving.


*Did you enjoy this exclusive breakdown? Follow for more real-world browser security deep-dives!*

Timeline

Published on: 07/27/2022 22:15:00 UTC
Last modified on: 08/15/2022 11:17:00 UTC