CVE-2021-21138
📋 TL;DR
This vulnerability is a use-after-free memory corruption flaw in Chrome's DevTools that allows a local attacker to potentially escape the browser's security sandbox via a specially crafted file. It affects Google Chrome users running versions before 88.0.4324.96. Successful exploitation could lead to arbitrary code execution with the privileges of the Chrome process.
💻 Affected Systems
- Google Chrome
📦 What is this software?
Chrome by Google
Google Chrome is the world's most popular web browser, used by over 3 billion users globally across Windows, macOS, Linux, Android, and iOS platforms. As a Chromium-based browser developed by Google, Chrome dominates the browser market with approximately 65% market share, making it a critical compon...
Learn more about Chrome →⚠️ Risk & Real-World Impact
Worst Case
Complete sandbox escape allowing attacker to execute arbitrary code on the host system with Chrome's process privileges, potentially leading to full system compromise.
Likely Case
Local attacker gains elevated privileges to execute code outside Chrome's sandbox, potentially installing malware or accessing sensitive system resources.
If Mitigated
With proper controls like Chrome's sandbox and updated versions, exploitation is prevented and the vulnerability has no impact.
🎯 Exploit Status
Requires local access and ability to execute a crafted file. Chrome's sandbox makes exploitation challenging but possible for skilled attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 88.0.4324.96 and later
Vendor Advisory: https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.html
Restart Required: Yes
Instructions:
1. Open Chrome and click the three-dot menu. 2. Go to Help > About Google Chrome. 3. Chrome will automatically check for updates and install version 88.0.4324.96 or later. 4. Click 'Relaunch' to restart Chrome with the update.
🔧 Temporary Workarounds
Disable DevTools
allPrevent access to Chrome DevTools which is required for exploitation
chrome://flags/#enable-devtools-experiments (set to Disabled)
Use enterprise policies to disable DevTools
Run Chrome with sandbox restrictions
allEnsure Chrome's sandbox is enabled and properly configured
chrome --no-sandbox (DO NOT USE - this disables protection)
Verify sandbox is enabled in chrome://sandbox/
🧯 If You Can't Patch
- Restrict local access to systems running vulnerable Chrome versions
- Implement application whitelisting to prevent execution of unauthorized files
🔍 How to Verify
Check if Vulnerable:
Check Chrome version: Open Chrome, go to chrome://version and verify version is below 88.0.4324.96Check Version:
google-chrome --version (Linux) or open chrome://version (all platforms)Verify Fix Applied:
Confirm Chrome version is 88.0.4324.96 or higher in chrome://version📡 Detection & Monitoring
Log Indicators:
- Chrome crash reports with memory corruption signatures
- Unexpected DevTools process activity
- Sandbox violation events in system logs
Network Indicators:
- Not applicable - local exploitation only
SIEM Query:
source="chrome" AND (event_type="crash" OR process_name="chrome_debug" OR message="sandbox")