CVE-2020-6492: Google Chrome Use After Free Vulnerability

CVE-2020-6492 Overview

CVE-2020-6492 is a Use After Free vulnerability in ANGLE (Almost Native Graphics Layer Engine), a critical graphics abstraction layer used by Google Chrome to translate OpenGL ES API calls to platform-specific graphics APIs. This memory corruption flaw in Chrome versions prior to 83.0.4103.97 allows a remote attacker to potentially escape the browser sandbox through a specially crafted HTML page, representing a severe threat to browser security.

Critical Impact
This vulnerability enables potential sandbox escape, allowing attackers to break out of Chrome's security isolation and execute arbitrary code on the underlying system with elevated privileges.

Affected Products

Google Chrome versions prior to 83.0.4103.97
All platforms running vulnerable Chrome versions (Windows, macOS, Linux)
Chromium-based browsers using the affected ANGLE component

Discovery Timeline

2021-11-02 - CVE-2020-6492 published to NVD
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-6492

Vulnerability Analysis

The Use After Free vulnerability exists within ANGLE, Chrome's graphics translation layer that enables cross-platform WebGL and OpenGL ES rendering. When Chrome processes certain WebGL or graphics operations through ANGLE, the component may incorrectly handle memory lifecycle management, leading to a condition where memory is accessed after it has been freed.

This vulnerability is classified as CWE-416 (Use After Free), a dangerous memory corruption issue that occurs when a program continues to use a pointer after the memory it references has been deallocated. In the context of ANGLE, this flaw can be triggered remotely by visiting a malicious webpage containing crafted HTML and WebGL content.

The most severe aspect of this vulnerability is its potential to enable sandbox escape. Chrome's sandbox is designed to isolate web content from the underlying operating system, but exploitation of this Use After Free could allow an attacker to bypass these protections entirely.

Root Cause

The root cause lies in improper memory management within ANGLE's graphics processing code. When handling specific graphics operations, ANGLE fails to properly track the lifecycle of allocated memory objects. This results in dangling pointer references where freed memory can be reallocated and overwritten with attacker-controlled data.

When the dangling pointer is subsequently dereferenced, the attacker-controlled data is treated as legitimate program data, potentially allowing arbitrary code execution within the renderer process. Combined with the sandbox escape capability, this creates a critical attack chain.

Attack Vector

The attack is network-based and requires user interaction—specifically, a victim must navigate to or be redirected to a malicious webpage. The attacker crafts an HTML page containing WebGL or graphics operations that trigger the Use After Free condition in ANGLE.

The exploitation flow involves:

Victim visits attacker-controlled webpage
Malicious page executes crafted WebGL/graphics operations
ANGLE processes the operations, triggering the Use After Free
Attacker achieves code execution within the renderer process
Sandbox escape allows full system compromise

The vulnerability can be triggered through crafted WebGL shader operations or specific ANGLE API calls that cause the graphics layer to mishandle memory allocation and deallocation sequences. Technical details are available in the Chromium Bug Report #1078375.

Detection Methods for CVE-2020-6492

Indicators of Compromise

Unexpected Chrome renderer process crashes or restarts when visiting websites
Anomalous WebGL rendering behavior or graphics errors in browser logs
Unusual memory access patterns in Chrome's graphics subsystem
Process spawning from Chrome that escapes the expected sandbox hierarchy

Detection Strategies

Monitor for Chrome renderer crashes with ANGLE-related stack traces
Implement browser version auditing to identify vulnerable Chrome installations (< 83.0.4103.97)
Deploy endpoint detection to identify exploitation attempts targeting graphics APIs
Analyze network traffic for suspicious HTML pages with complex WebGL operations

Monitoring Recommendations

Enable Chrome crash reporting and analyze ANGLE-related crash dumps
Monitor endpoint processes for unexpected child processes spawned from Chrome
Implement web content inspection for known exploit patterns targeting ANGLE
Track browser version compliance across the organization to ensure timely patching

How to Mitigate CVE-2020-6492

Immediate Actions Required

Update Google Chrome to version 83.0.4103.97 or later immediately
Enable automatic browser updates to receive security patches promptly
Consider restricting WebGL on untrusted websites as a temporary measure
Audit all Chromium-based browsers in the environment for the vulnerable component

Patch Information

Google has released a security update that addresses this vulnerability in Chrome version 83.0.4103.97. The patch corrects the memory management issues in ANGLE that allowed the Use After Free condition. Organizations should prioritize updating to the patched version.

For detailed information about the security update, refer to the Google Chrome Desktop Update announcement.

Workarounds

Disable WebGL in Chrome via chrome://flags/#disable-webgl as a temporary mitigation
Use browser isolation solutions to execute web content in sandboxed virtual environments
Implement web filtering to block access to known malicious domains
Consider using enterprise browser policies to restrict graphics API access on sensitive systems

bash

# Chrome enterprise policy example to disable WebGL (Windows Registry)
# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome
# WebGLAllowed REG_DWORD 0

# Linux/macOS managed preferences
# Set WebGLAllowed to false in Chrome managed policies JSON