Google Chrome: Which of the 21 Vulnerabilities Allowed Attackers to Crash Your PC? Full Analysis & Fixes

By CyberDudeBivash • October 02, 2025, 05:10 PM IST • Urgent Security Advisory

Google has just released an emergency security update for its Chrome browser, patching a total of 21 vulnerabilities. While many of these are routine fixes, this update is critical because it includes a patch for a **zero-day vulnerability that is being actively exploited in the wild**. The flaw, a high-severity Use-After-Free bug, can be triggered by a malicious website to crash your browser and, in a worst-case scenario, could lead to a full system takeover. If you are a Chrome user on Windows, Mac, or Linux, you are currently vulnerable. This is not a routine update; it is an emergency patch that you need to apply immediately. This is our full analysis of the critical flaw and the exact steps you need to take to get protected NOW.

Disclosure: This is a public service security advisory. It contains affiliate links to security solutions that provide defense-in-depth against web-based threats. Your support helps fund our independent research.

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Threat Report: Table of Contents

Chapter 1: The ‘PC Crasher’ — Deep Dive into the Mojo Use-After-Free (CVE-2025-11311)

The most serious flaw in this update is the zero-day tracked as **CVE-2025-11311**. This is a **Use-After-Free (UAF)** vulnerability in Mojo, which is Chrome’s underlying framework for inter-process communication (IPC). In simple terms, it’s the messaging system that allows the different parts of the browser (like the renderer, the GPU process, and the main browser process) to talk to each other securely.

How the Exploit Works:

A UAF is a memory corruption bug. Imagine the browser gives a piece of code a key to a hotel room (a pointer to a memory address). The code finishes its work, the room is cleaned and the memory is “freed.” However, due to the bug, the code keeps a copy of the old key. An attacker on a malicious website can then quickly “rent” that same room (allocate that memory). When the original code uses its old, invalid key, it doesn’t find its own data; it finds the attacker’s malicious code. At a minimum, this causes a conflict that crashes the browser. For a skilled attacker, this is a direct path to escaping the browser’s sandbox and achieving **Remote Code Execution (RCE)** on the underlying PC.

Chapter 2: A Look at the Other High-Severity Bugs Patched

While the zero-day gets the headlines, the update also fixes a host of other dangerous flaws. The 21 patches include several other high-severity vulnerabilities, including:

**Heap buffer overflows in the V8 JavaScript engine:** These could also be exploited for arbitrary code execution.
**Integer overflow in the Skia 2D graphics library:** This could be triggered by a malicious image or website element.
**Insufficient policy enforcement in WebRTC:** This could potentially allow a malicious site to access your camera or microphone without proper permission.
**Multiple vulnerabilities in the open-source libraries** that Chrome uses, such as libpng and ffmpeg.

This long list underscores the immense complexity of a modern web browser and the constant effort required to keep it secure.

Chapter 3: THE DEFENDER’S PLAYBOOK — How to Update and Secure Your Chrome Browser NOW

Patching this flaw is simple, but you must complete the final step for it to work.

Step 1: Open the “About Google Chrome” Page

Click the three vertical dots in the top-right corner of your Chrome browser. Go to **Help**, and then click on **About Google Chrome**. You can also simply type `chrome://settings/help` into your address bar and hit Enter.

Step 2: Let Chrome Download the Update

As soon as you open the “About” page, Chrome will automatically check for new updates and begin downloading the patched version (129.0.6649.212 or higher).

Step 3: RELAUNCH Your Browser (CRITICAL STEP)

Once the download is complete, a **”Relaunch”** button will appear. Your browser is **NOT** protected until you click this button and restart Chrome. Simply closing and reopening the window is not enough. You must click the Relaunch button to finalize the update.

An update is a great defense, but a better defense is never visiting the malicious site in the first place. A powerful security suite like **Kaspersky Premium** includes a “Safe Browsing” feature that uses real-time threat intelligence to block you from accessing known malicious and phishing websites, preventing the exploit from ever reaching your browser.

Chapter 4: The Strategic Response — Why Browser Security is Endpoint Security

This incident is a critical reminder that for most users today, the web browser *is* the operating system. It’s where we do our banking, our communication, and our work. A compromise of the browser is a compromise of the entire endpoint.

A mature security strategy, therefore, must be built on the principle of **Defense-in-Depth**. You cannot rely solely on Google’s engineers to keep you safe. Your strategy must include:

**Prompt Patching:** A culture of applying critical updates immediately.
**Web Filtering:** A layer of defense that blocks malicious sites before the browser even connects.
**Endpoint Protection (EDR):** A last line of defense on the machine itself that can detect the malicious activity that happens *if* a browser exploit is successful. You can learn more in our **Ultimate Guide to EDR**.

Relying on any single layer is a recipe for failure. A multi-layered defense is the only path to resilience.

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About the Author

CyberDudeBivash is a cybersecurity strategist and researcher with over 15 years of experience in exploit analysis, browser security, and incident response. He provides strategic advisory services to CISOs and boards across the APAC region. [Last Updated: October 02, 2025]

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