CVE-2021-21148: Google Chrome Buffer Overflow Vulnerability

CVE-2021-21148 Overview

CVE-2021-21148 is a heap buffer overflow vulnerability in the V8 JavaScript engine used by Google Chrome. This vulnerability allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. The flaw exists in Chrome versions prior to 88.0.4324.150 and has been actively exploited in the wild, earning its place in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Critical Impact
This vulnerability enables remote code execution through heap corruption when a user visits a malicious webpage, potentially allowing complete system compromise. Active exploitation has been confirmed in the wild.

Affected Products

Google Chrome (versions prior to 88.0.4324.150)
Fedora Project Fedora 32 and 33
Debian Linux 10.0

Discovery Timeline

2021-02-09 - CVE-2021-21148 published to NVD
2025-10-24 - Last updated in NVD database

Technical Details for CVE-2021-21148

Vulnerability Analysis

CVE-2021-21148 is classified under CWE-787 (Out-of-Bounds Write), indicating that the vulnerability allows writing data beyond the boundaries of allocated memory buffers. The V8 JavaScript engine, which powers Chrome's JavaScript execution, contains a flaw in its memory handling routines that can be triggered through specially crafted JavaScript code embedded in an HTML page.

The heap buffer overflow occurs when V8 processes certain JavaScript operations, causing the engine to write data outside the bounds of a heap-allocated buffer. This memory corruption can be leveraged by attackers to achieve arbitrary code execution within the context of the browser process.

Root Cause

The root cause lies in improper boundary checking within V8's array handling mechanisms. When processing specific JavaScript array operations, V8 fails to properly validate buffer sizes, allowing an attacker to craft JavaScript that triggers an out-of-bounds write condition. This type of vulnerability is particularly dangerous in JavaScript engines due to the complexity of modern JIT (Just-In-Time) compilation and optimization techniques.

Attack Vector

The attack vector is network-based and requires user interaction—specifically, the victim must navigate to a malicious webpage containing the crafted HTML and JavaScript payload. Once the page is loaded, the exploit code executes within the browser's V8 engine, triggering the heap corruption. Successful exploitation can lead to arbitrary code execution with the privileges of the current user.

The attack requires no authentication or special privileges beyond convincing a user to visit a malicious URL. This can be accomplished through phishing emails, malicious advertisements, compromised websites, or watering hole attacks.

Detection Methods for CVE-2021-21148

Indicators of Compromise

Unusual Chrome renderer process crashes or unexpected memory consumption patterns
Network connections to suspicious domains following Chrome browser activity
Presence of suspicious JavaScript files or HTML pages in browser cache
Anomalous child process spawning from Chrome browser processes

Detection Strategies

Monitor for Chrome versions older than 88.0.4324.150 across the enterprise environment
Implement browser isolation technologies to contain potential exploits
Deploy endpoint detection and response (EDR) solutions capable of detecting heap spray and memory corruption techniques
Enable Chrome's Site Isolation feature to limit the impact of renderer exploits

Monitoring Recommendations

Review browser crash reports for patterns indicating exploitation attempts
Monitor network traffic for connections to known malicious infrastructure associated with browser exploits
Enable enhanced logging for Chrome browser events on critical systems
Correlate browser process behavior with threat intelligence feeds for known exploitation patterns

How to Mitigate CVE-2021-21148

Immediate Actions Required

Update Google Chrome to version 88.0.4324.150 or later immediately
Enable automatic updates for Chrome browsers across all managed endpoints
Apply Debian security update DSA-4858 for Debian Linux 10.0 systems
Apply Fedora package updates for Fedora 32 and 33 systems

Patch Information

Google released a stable channel update for Chrome desktop on February 4, 2021, addressing this vulnerability. The fix is included in Chrome version 88.0.4324.150 and all subsequent releases. Organizations should ensure all Chrome installations are updated to this version or later.

For additional details, refer to the Google Chrome Update Advisory. Linux distribution users should apply vendor-specific security updates:

Workarounds

Implement web content filtering to block access to known malicious sites
Consider using browser isolation solutions for high-risk users or when accessing untrusted content
Disable JavaScript execution on untrusted websites using browser extensions or enterprise policies
Deploy network-level protections to detect and block exploit delivery attempts

bash

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

# Force Chrome update on managed systems
# Ensure the following policies are configured:
# AutoUpdateCheckPeriodMinutes: 60
# RelaunchNotification: 2
# RelaunchNotificationPeriod: 604800000