CVE-2021-30563: Google Chrome V8 RCE Vulnerability

CVE-2021-30563 Overview

CVE-2021-30563 is a type confusion vulnerability in the V8 JavaScript engine used by Google Chrome. This vulnerability exists in versions prior to 91.0.4472.164 and allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. Type confusion vulnerabilities occur when a program allocates an object of one type but subsequently accesses it using a type that is incompatible, leading to memory corruption and potential code execution.

Critical Impact

This vulnerability has been actively exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities catalog. Successful exploitation could allow attackers to execute arbitrary code within the browser context, potentially leading to complete system compromise.

Affected Products

• Google Chrome versions prior to 91.0.4472.164
• All platforms running vulnerable Chrome versions (Windows, macOS, Linux)
• Chromium-based browsers that incorporate the affected V8 engine version

Discovery Timeline

• 2021-08-03 - CVE-2021-30563 published to NVD
• 2025-10-24 - Last updated in NVD database

Technical Details for CVE-2021-30563

Vulnerability Analysis

This vulnerability is classified as CWE-843 (Access of Resource Using Incompatible Type - Type Confusion). The flaw resides in the V8 JavaScript engine, which is responsible for executing JavaScript code within Chrome. Type confusion vulnerabilities in V8 are particularly dangerous because they can be triggered simply by visiting a malicious webpage.

The vulnerability allows for heap corruption, which can be leveraged by attackers to achieve arbitrary code execution. When the V8 engine incorrectly handles type information for JavaScript objects, it may access memory using the wrong type assumptions, leading to out-of-bounds reads or writes.

Root Cause

The root cause is improper type handling within the V8 JavaScript engine. When processing certain JavaScript constructs, V8 fails to properly validate or track the type of an object, allowing an attacker to craft JavaScript code that causes the engine to treat one type of object as another. This type confusion leads to heap memory corruption as the engine accesses memory regions with incorrect size or structure assumptions.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker can exploit this vulnerability by:

1. Hosting a malicious HTML page containing specially crafted JavaScript code
2. Enticing a victim to visit the malicious webpage (via phishing, malvertising, or compromised websites)
3. When the page loads, the crafted JavaScript triggers the type confusion in V8
4. The resulting heap corruption can be leveraged to gain code execution within the browser's renderer process

The vulnerability is particularly concerning because it requires no special permissions or authentication—simply visiting a malicious website is sufficient to trigger the exploit.

Detection Methods for CVE-2021-30563

Indicators of Compromise

• Unusual browser crashes or hangs when visiting specific websites
• Suspicious network connections originating from browser processes
• Unexpected child processes spawned by Chrome or Chromium-based browsers
• Evidence of memory corruption or unusual memory access patterns in browser crash dumps

Detection Strategies

• Monitor for browser version strings indicating Chrome versions below 91.0.4472.164
• Implement endpoint detection rules to identify V8 exploitation patterns
• Deploy network-based detection for known malicious pages targeting this vulnerability
• Review browser crash reports for heap corruption indicators specific to V8

Monitoring Recommendations

• Enable Chrome's built-in Safe Browsing feature to block known malicious URLs
• Monitor endpoint telemetry for unusual browser behavior or exploitation attempts
• Track browser version compliance across the enterprise to identify unpatched systems
• Implement network monitoring to detect connections to known threat infrastructure

How to Mitigate CVE-2021-30563

Immediate Actions Required

• Update Google Chrome to version 91.0.4472.164 or later immediately
• Enable automatic updates for Chrome to receive future security patches
• Audit all systems to identify and remediate instances of vulnerable Chrome versions
• Consider implementing browser isolation for high-risk users until patching is complete

Patch Information

Google has addressed this vulnerability in Chrome version 91.0.4472.164. The fix is available through the Google Chrome Desktop Update. Organizations should prioritize deployment of this update given the confirmed active exploitation of this vulnerability. Additional technical details are available in Chrome Bug Report #1228407.

This vulnerability is tracked in the CISA Known Exploited Vulnerabilities Catalog, which mandates federal agencies remediate within specified timeframes.

Workarounds

• Disable JavaScript in Chrome settings as a temporary measure (impacts functionality)
• Use browser isolation technology to contain potential exploitation
• Implement strict web filtering to block access to untrusted or unknown websites
• Consider using alternative browsers until Chrome can be updated

# Verify Chrome version on Linux/macOS
google-chrome --version

# Force Chrome update check
# Navigate to chrome://settings/help in the browser
# Or use enterprise deployment tools to push the latest version