CVE-2021-21132
📋 TL;DR
This vulnerability in Chrome DevTools allowed malicious Chrome extensions to escape the browser's security sandbox. Attackers could potentially execute arbitrary code on the victim's system. All Chrome users prior to version 88.0.4324.96 were affected.
💻 Affected Systems
- Google Chrome
- Chromium-based browsers
- Microsoft Edge (Chromium-based)
📦 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 →Edge Chromium by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via arbitrary code execution with user privileges, allowing data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malicious extension could access local files, system resources, and execute commands outside browser sandbox, leading to data exfiltration or credential theft.
If Mitigated
With updated Chrome and proper extension vetting, risk is limited to theoretical exploitation attempts that would be blocked.
🎯 Exploit Status
Exploitation requires user interaction to install malicious extension. No public exploit code available, but technical details were disclosed in bug reports.
🛠️ 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 menu > Help > About Google Chrome. 2. Chrome will automatically check for updates and install version 88.0.4324.96 or later. 3. Click 'Relaunch' to restart Chrome with the fix applied.
🔧 Temporary Workarounds
Disable Chrome DevTools
allPrevent access to DevTools which was the attack vector
Not applicable via command line - use Chrome policies or disable via settings
Restrict Extension Installation
allOnly allow extensions from trusted sources and require admin approval
Windows: Configure via Group Policy 'ExtensionInstallWhitelist'
macOS/Linux: Use Chrome Enterprise policies
🧯 If You Can't Patch
- Implement application allowlisting to block Chrome execution entirely
- Deploy network filtering to block extension downloads from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check Chrome version in menu > Help > About Google Chrome. If version is below 88.0.4324.96, system is vulnerable.Check Version:
chrome://version/ or on command line: google-chrome --version (Linux), 'Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\chrome.exe"' (Windows)Verify Fix Applied:
Confirm Chrome version is 88.0.4324.96 or higher. Test by attempting to reproduce the DevTools sandbox escape (not recommended in production).📡 Detection & Monitoring
Log Indicators:
- Chrome crash reports with DevTools process anomalies
- Unexpected extension installation events
- Process creation from Chrome with unusual parent-child relationships
Network Indicators:
- Downloads of Chrome extensions from unusual sources
- Outbound connections from Chrome to unexpected destinations post-extension installation
SIEM Query:
process_name:"chrome.exe" AND (parent_process:"chrome.exe" AND command_line:"*type=extension*" OR command_line:"*--enable-devtools-experiments*")🔗 References
- https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.html
- https://crbug.com/1128206
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-21132
- https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.html
- https://crbug.com/1128206
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-21132
