CVE-2021-30554: Google Chrome WebGL Use-After-Free Flaw

CVE-2021-30554 Overview

CVE-2021-30554 is a use-after-free vulnerability in the WebGL component of Google Chrome prior to version 91.0.4472.114. This memory corruption flaw allows a remote attacker to potentially exploit heap corruption via a crafted HTML page, leading to arbitrary code execution within the context of the browser.

Critical Impact

This vulnerability is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. Successful exploitation can lead to complete compromise of affected systems through heap corruption attacks targeting the WebGL rendering engine.

Affected Products

• Google Chrome versions prior to 91.0.4472.114
• Fedora Project Fedora 33
• Fedora Project Fedora 34

Discovery Timeline

• July 2, 2021 - CVE-2021-30554 published to NVD
• October 24, 2025 - Last updated in NVD database

Technical Details for CVE-2021-30554

Vulnerability Analysis

This vulnerability exists within Google Chrome's WebGL implementation, which provides JavaScript API access to GPU-accelerated graphics rendering. The use-after-free condition (CWE-416) occurs when the WebGL subsystem continues to reference memory after it has been freed, creating a dangling pointer situation that can be weaponized by attackers.

When a victim visits a malicious webpage containing specially crafted HTML and JavaScript, the attacker can manipulate WebGL objects to trigger the use-after-free condition. This corrupts heap memory structures, potentially allowing the attacker to hijack control flow and execute arbitrary code with the privileges of the browser process.

The attack requires user interaction (visiting a malicious page) but can be delivered through common attack vectors such as phishing emails, malicious advertisements, or compromised websites. Given the network-accessible nature of web browsers, this vulnerability presents a significant attack surface for drive-by download attacks.

Root Cause

The root cause is a use-after-free memory safety error in the WebGL component of the Chromium rendering engine. Specifically, the vulnerability stems from improper lifecycle management of WebGL objects, where references to freed memory are not properly invalidated. This allows subsequent operations to access deallocated heap memory, corrupting memory structures or enabling arbitrary read/write primitives.

Attack Vector

The attack vector is network-based, requiring a victim to navigate to an attacker-controlled or compromised website serving malicious HTML content. The attack flow typically involves:

1. Attacker crafts a malicious HTML page with JavaScript that manipulates WebGL objects
2. Victim visits the malicious page (via phishing, compromised ads, or watering hole attacks)
3. JavaScript triggers the use-after-free condition in Chrome's WebGL implementation
4. Heap corruption occurs, potentially leading to code execution
5. Attacker gains code execution within the browser's sandboxed renderer process

Due to the heap corruption nature of this vulnerability, exploitation may involve heap spray techniques to achieve reliable code execution. Further sandbox escape vulnerabilities may be chained to achieve full system compromise.

Detection Methods for CVE-2021-30554

Indicators of Compromise

• Unusual Chrome renderer process crashes or memory corruption errors
• Network connections to suspicious domains serving malicious HTML/JavaScript
• Anomalous WebGL API calls or unusually complex WebGL shader operations
• Browser crash dumps containing heap corruption signatures in WebGL-related functions

Detection Strategies

• Monitor for Google Chrome versions below 91.0.4472.114 across the enterprise
• Implement network-based detection for known malicious domains exploiting this vulnerability
• Deploy endpoint detection solutions capable of identifying use-after-free exploitation patterns
• Review browser crash reports for indicators of heap corruption in WebGL components

Monitoring Recommendations

• Enable Chrome's built-in crash reporting to collect and analyze crash dumps centrally
• Monitor for unusual JavaScript execution patterns related to WebGL object manipulation
• Track browser version deployment across endpoints to identify unpatched systems
• Implement web filtering to block access to known malicious domains

How to Mitigate CVE-2021-30554

Immediate Actions Required

• Update Google Chrome to version 91.0.4472.114 or later immediately
• Enable automatic updates for Google Chrome across all managed endpoints
• Consider temporarily disabling WebGL in Chrome via enterprise policies if immediate patching is not possible
• Review the CISA Known Exploited Vulnerabilities catalog for additional guidance

Patch Information

Google addressed this vulnerability in Chrome version 91.0.4472.114, released on June 17, 2021. The fix resolves the improper memory management in the WebGL component that led to the use-after-free condition.

Organizations should reference the following resources for patch information:

• Chrome Stable Channel Update - Official Google release notes
• Chromium Bug Report #1219857 - Technical bug details
• Gentoo GLSA 202107-06 - Gentoo security advisory

Fedora users should apply the latest Chromium packages from the official repositories as detailed in the Fedora Package Announcements.

Workarounds

• Disable WebGL in Chrome by navigating to chrome://flags/#disable-webgl and setting it to Disabled
• Implement enterprise browser policies to restrict WebGL functionality until patching is complete
• Use network-level controls to block access to untrusted websites
• Consider deploying browser isolation solutions to contain potential exploitation attempts

# Chrome Enterprise Policy to disable WebGL (Windows Registry)
# Create the following registry key to disable WebGL across managed Chrome installations:
# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome
# Value: WebGLDisabled = 1 (DWORD)

# For Linux/macOS managed environments, add to Chrome policy JSON:
# {
#   "WebGLDisabled": true
# }