CVE-2021-30517: Google Chrome V8 RCE Vulnerability

CVE-2021-30517 Overview

CVE-2021-30517 is a type confusion vulnerability in the V8 JavaScript engine used by Google Chrome prior to version 90.0.4430.212. This vulnerability allows a remote attacker to potentially exploit heap corruption via a crafted HTML page, enabling remote code execution in the context of the browser.

Critical Impact

Remote attackers can exploit this type confusion vulnerability to corrupt heap memory and potentially execute arbitrary code on victim systems simply by convincing users to visit a malicious webpage.

Affected Products

• Google Chrome versions prior to 90.0.4430.212
• Fedora 33 (Chromium package)
• Fedora 34 (Chromium package)

Discovery Timeline

• June 4, 2021 - CVE-2021-30517 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2021-30517

Vulnerability Analysis

This vulnerability is classified as CWE-843 (Access of Resource Using Incompatible Type, also known as Type Confusion). Type confusion vulnerabilities occur when a program accesses a resource using an incompatible type, leading to logical errors that can result in memory corruption.

In the context of V8, Chrome's JavaScript engine, type confusion can occur when the engine incorrectly interprets the type of an object during runtime. This misinterpretation can lead to out-of-bounds memory access or heap corruption, as the engine operates on memory assuming it contains data structured differently than what is actually present.

The attack requires user interaction—specifically, a victim must be lured to visit a specially crafted HTML page containing malicious JavaScript designed to trigger the type confusion condition in V8. Once triggered, the attacker can potentially leverage the resulting heap corruption to achieve arbitrary code execution within the browser's sandbox.

Root Cause

The root cause of CVE-2021-30517 lies in improper type handling within the V8 JavaScript engine. V8 performs just-in-time (JIT) compilation and various optimizations that rely on type inference. When these type assumptions are incorrect or can be manipulated by attacker-controlled input, the engine may operate on memory using the wrong type interpretation.

This specific type confusion vulnerability allows an attacker to craft JavaScript that causes V8 to mishandle object types during execution, resulting in heap memory corruption that can be exploited for code execution.

Attack Vector

The attack vector for this vulnerability is network-based and requires user interaction. An attacker would need to:

1. Create a malicious webpage containing specially crafted JavaScript code designed to trigger the type confusion in V8
2. Lure a victim to visit the malicious page (via phishing, malicious advertisements, or compromised legitimate websites)
3. When the victim's Chrome browser (versions prior to 90.0.4430.212) processes the malicious JavaScript, the type confusion triggers heap corruption
4. The attacker can potentially leverage this corruption to execute arbitrary code within the browser's renderer process

The vulnerability details are tracked in Chromium Bug Report #1203122. Since verified exploit code is not publicly available, organizations should refer to the official security advisories for technical implementation details.

Detection Methods for CVE-2021-30517

Indicators of Compromise

• Unusual browser crashes or renderer process terminations, particularly when visiting untrusted websites
• Unexpected memory consumption patterns in Chrome's renderer processes
• Detection of suspicious JavaScript code attempting to manipulate object types in anomalous ways
• Signs of sandbox escape attempts or unusual process spawning from browser processes

Detection Strategies

• Deploy browser version monitoring to identify systems running Chrome versions prior to 90.0.4430.212
• Implement endpoint detection rules to identify heap corruption exploitation patterns in browser processes
• Monitor for unusual V8 engine behavior through crash telemetry and browser diagnostics
• Utilize web filtering to block access to known malicious domains serving exploit pages

Monitoring Recommendations

• Enable Chrome's built-in crash reporting and monitor for patterns indicative of exploitation attempts
• Implement network-level monitoring to detect connections to suspicious or newly registered domains
• Configure SIEM rules to correlate browser crashes with recent navigation to untrusted URLs
• Maintain visibility into browser version deployment across the enterprise

How to Mitigate CVE-2021-30517

Immediate Actions Required

• Update Google Chrome to version 90.0.4430.212 or later immediately across all systems
• For Fedora users, apply the latest Chromium package updates via the package manager
• Restrict browsing to trusted websites until patches are applied
• Consider implementing browser isolation technologies for high-risk users

Patch Information

Google has released a security patch addressing this vulnerability in Chrome version 90.0.4430.212. The fix was announced in the Google Chrome Stable Channel Update. Fedora has also released updated packages for Fedora 33 and Fedora 34 as documented in the Fedora Package Announcements. Additionally, Gentoo users should review GLSA 2021-07-06 for patching guidance.

Workarounds

• Enable Chrome's Site Isolation feature to limit the impact of renderer process compromise
• Disable JavaScript on untrusted sites using browser extensions or policies (may impact functionality)
• Implement network-level blocking of known malicious domains and suspicious content
• Consider using alternative browsers temporarily until Chrome can be updated in your environment

# Configuration example - Verify Chrome version on Linux systems
google-chrome --version

# Update Chrome on Fedora systems
sudo dnf update chromium

# Enable site isolation via Chrome enterprise policy
# Add to /etc/chromium/policies/managed/policy.json
{
  "SitePerProcess": true,
  "IsolateOrigins": "*.example.com"
}