CVE-2021-30632: Google Chrome V8 RCE Vulnerability

CVE-2021-30632 Overview

CVE-2021-30632 is an out-of-bounds write vulnerability in the V8 JavaScript engine used by Google Chrome prior to version 93.0.4577.82. This flaw allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. The vulnerability, classified as CWE-787 (Out-of-bounds Write), represents a critical memory safety issue in Chrome's core JavaScript execution engine that has been actively exploited in the wild.

Critical Impact

This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation in real-world attacks. Attackers can leverage this flaw to achieve arbitrary code execution on victim systems simply by convincing users to visit a malicious webpage.

Affected Products

• Google Chrome versions prior to 93.0.4577.82
• Fedora Project Fedora 33
• Fedora Project Fedora 35

Discovery Timeline

• October 8, 2021 - CVE-2021-30632 published to NVD
• October 24, 2025 - Last updated in NVD database

Technical Details for CVE-2021-30632

Vulnerability Analysis

This vulnerability exists within V8, Google Chrome's high-performance JavaScript and WebAssembly engine. The flaw involves a type confusion issue in V8's Just-In-Time (JIT) compiler, which leads to an out-of-bounds write condition. When the JIT compiler incorrectly handles certain object types during optimization, it can write data beyond the boundaries of allocated heap memory.

The heap corruption that results from this out-of-bounds write can be weaponized to achieve arbitrary code execution. An attacker who successfully exploits this vulnerability gains the ability to execute code with the same privileges as the Chrome browser process, potentially leading to full system compromise depending on the browser's sandbox configuration and any sandbox escape techniques employed.

Root Cause

The root cause of CVE-2021-30632 lies in a type confusion vulnerability within V8's JIT compiler. During the compilation of JavaScript code to native machine code, the JIT compiler makes assumptions about object types to optimize performance. When these assumptions are violated through carefully crafted JavaScript, the compiler can generate code that performs out-of-bounds memory writes. This class of vulnerability is particularly dangerous in JavaScript engines because the attacker has fine-grained control over memory layout through JavaScript object manipulation.

Attack Vector

The attack vector for this vulnerability is network-based, requiring user interaction. An attacker must craft a malicious HTML page containing JavaScript code designed to trigger the type confusion in V8's JIT compiler. The attack scenario typically involves:

1. Attacker creates a malicious webpage with specially crafted JavaScript
2. Victim is lured to visit the page via phishing, watering hole attacks, or malicious advertisements
3. The JavaScript executes in the victim's browser, triggering the type confusion
4. The resulting out-of-bounds write corrupts heap memory in a controlled manner
5. Attacker achieves arbitrary code execution within the browser's renderer process

Technical details regarding the JIT compiler type confusion are documented in the Packet Storm Exploit Report and the Chromium Bug Report.

Detection Methods for CVE-2021-30632

Indicators of Compromise

• Unusual Chrome renderer process crashes or unexpected behavior following visits to unknown websites
• Memory corruption artifacts or crash dumps indicating heap corruption in the Chrome V8 process
• Network connections to suspicious domains immediately before Chrome process anomalies
• JavaScript execution patterns consistent with heap spraying or JIT spray techniques

Detection Strategies

• Deploy endpoint detection solutions capable of monitoring Chrome process behavior for exploitation attempts
• Implement network-based detection for known malicious domains serving CVE-2021-30632 exploits
• Monitor for Chrome crash reports that indicate V8 memory corruption signatures
• Utilize browser telemetry to identify visits to potentially malicious websites with embedded exploit code

Monitoring Recommendations

• Enable Chrome's enhanced Safe Browsing feature to receive protection against known malicious sites
• Configure endpoint detection and response (EDR) solutions to monitor Chrome child processes for suspicious activity
• Implement logging of browser extension installations and JavaScript execution anomalies
• Review Chrome enterprise policies to ensure automatic updates are enabled

How to Mitigate CVE-2021-30632

Immediate Actions Required

• Update Google Chrome to version 93.0.4577.82 or later immediately across all endpoints
• Verify that automatic Chrome updates are enabled and functioning properly
• For Fedora systems, apply the latest security updates via the package manager
• Consider temporarily restricting access to untrusted websites until patching is complete

Patch Information

Google released Chrome version 93.0.4577.82 on September 13, 2021, which addresses this vulnerability. The fix was announced in the Google Chrome Update Announcement. Fedora users should apply updates through their distribution's package management system as referenced in the Fedora Package Announcements.

Given that this vulnerability is listed in the CISA Known Exploited Vulnerabilities Catalog, federal agencies are required to remediate this vulnerability according to CISA deadlines.

Workarounds

• Disable JavaScript execution in Chrome via settings, though this significantly impacts web functionality
• Use browser isolation or virtual desktop infrastructure to contain potential exploits
• Implement network-level filtering to block access to known malicious domains
• Consider using alternative browsers temporarily while awaiting Chrome updates in managed environments

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

# Update Chrome on Fedora
sudo dnf update chromium

# Force Chrome update check (launch Chrome with)
google-chrome --check-for-update-interval=1