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Introduction

Security flaws in popular web browsers can lead to serious risks, especially when remote attackers can exploit them just by luring users to a malicious website. One such vulnerability, CVE-2022-1855, existed in Google Chrome’s Messaging component. Discovered by Google’s own security researchers, this issue is a classic use-after-free (UAF) bug, and potentially lets an attacker run code on the victim’s device. In this deep dive, we’ll break down what this CVE means, include some code snippets, share links to official resources, and explain a plausible exploitation scenario — all in simple, clear terms.

Possible Damage: Heap corruption, which can potentially lead to arbitrary code execution

A "use-after-free" bug happens when a program keeps using an object in memory after it’s already been deleted (freed). In complex applications like browsers, this can cause memory corruption, and sometimes attackers can abuse this to run their own code.

Report Date: Mid-2022

- Patched in: Chrome 102..5005.61 (see Chrome Release log)
- Reference: Chromium Issue 1314106

The Vulnerability

The bug lived in Chrome’s Messaging API implementation. Mismanagement in the messaging lifecycle caused some objects to be used after they had already been deleted, opening the door to heap corruption.

Here’s a simple illustration of what a use-after-free might look like (in C++-like pseudocode)

MessagingObject* obj = new MessagingObject();
// ... object gets used somewhere
delete obj; // object is freed
obj->sendMessage("Hello!"); // use-after-free: still trying to use it!

In reality, browsers juggle complex objects and memory. Under certain conditions, especially with clever JavaScript, it was possible to free a Messaging object (or part of it), but Chrome might try to use it immediately after -- thus triggering the bug, and giving attackers a memory corruption primitive.

Proof-of-Concept (PoC) Example

Though the exact exploit code is not public (for security reasons), a generic example using JavaScript could look like:

// This is a simplified and hypothetical explanation
var channel = new MessageChannel();
channel.port1.onmessage = function(e) {
    // Free some resource tied to messaging
    channel.port1.close();
    // Try to trigger a use of the now-freed structure
    // by posting message again
    channel.port1.postMessage("Trigger");
};
channel.port2.postMessage("Exploit");

The attacker could carefully control object lifetimes and force Chrome to access freed memory.

User visits the page with a vulnerable Chrome version (<102..5005.61).

3. The page manipulates MessagePorts and objects so Chrome re-uses deleted memory. Sometimes, that memory may have attacker-controlled content or pointers.
4. This can cause heap corruption, and in advanced attacks, carefully crafted data can lead to arbitrary code execution.

While exploitation is tough (a browser needs many protections bypassed), skilled attackers have used UAF bugs for full exploit chains.

Official Resources

- Chrome Releases: Security fixes
- Chromium Issue 1314106 Tracker (limited details)
- NVD’s listing for CVE-2022-1855

Enable automatic updates: Most browsers update automatically, but check your settings.

- Practice safe browsing: Avoid mysterious links and disable JavaScript on sites you deeply distrust.

Conclusion

CVE-2022-1855 is a prime example of how subtle memory bugs can lead to big security holes. Thanks to Chrome’s security team, the bug was patched rapidly, but if you haven’t updated your browser, you’re at risk. Keep your software up-to-date and stay aware of these behind-the-scenes threats.

If you want to learn more about use-after-free bugs, check out Google's Project Zero blog.

Timeline

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