CVE-2021-21207
📋 TL;DR
This is a use-after-free vulnerability in Chrome's IndexedDB component that allows sandbox escape. Attackers can exploit it by convincing users to install a malicious Chrome extension, potentially gaining elevated privileges. All Chrome users prior to version 90.0.4430.72 are affected.
💻 Affected Systems
- Google Chrome
- Chromium-based browsers
📦 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...
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⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via sandbox escape, allowing attackers to execute arbitrary code with elevated privileges on the victim's system.
Likely Case
Limited sandbox escape leading to data theft, privilege escalation, or installation of persistent malware via malicious extensions.
If Mitigated
No impact if Chrome is updated to patched version or if users don't install malicious extensions.
🎯 Exploit Status
Exploitation requires convincing user to install malicious extension. No public exploit code available but vulnerability is actively patched.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 90.0.4430.72 and later
Vendor Advisory: https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop_14.html
Restart Required: Yes
Instructions:
1. Open Chrome 2. Click menu (three dots) → Help → About Google Chrome 3. Chrome will automatically check for and install updates 4. Click 'Relaunch' to restart Chrome
🔧 Temporary Workarounds
Disable Chrome Extensions
allTemporarily disable all Chrome extensions to prevent exploitation via malicious extensions
chrome://extensions/ → Toggle off all extensions
Restrict Extension Installation
windowsConfigure Chrome to only allow extensions from Chrome Web Store
Group Policy: ExtensionInstallSources = https://chrome.google.com/webstore/detail/*
🧯 If You Can't Patch
- Implement application whitelisting to block Chrome execution
- Deploy network filtering to block extension downloads from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check Chrome version: If version is less than 90.0.4430.72, system is vulnerableCheck Version:
google-chrome --version (Linux) or chrome://version (all platforms)Verify Fix Applied:
Confirm Chrome version is 90.0.4430.72 or higher📡 Detection & Monitoring
Log Indicators:
- Unusual extension installation events
- Chrome crash reports with IndexedDB-related errors
Network Indicators:
- Downloads of Chrome extension files (.crx) from non-Google domains
SIEM Query:
source="chrome" AND (event="extension_install" OR event="crash") AND version<"90.0.4430.72"🔗 References
- https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop_14.html
- https://crbug.com/1185732
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EAJ42L4JFPBJATCZ7MOZQTUDGV4OEHHG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3GZ42MYPGD35V652ZPVPYYS7A7LVXVY/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/
- https://security.gentoo.org/glsa/202104-08
- https://www.debian.org/security/2021/dsa-4906
- https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop_14.html
- https://crbug.com/1185732
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EAJ42L4JFPBJATCZ7MOZQTUDGV4OEHHG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3GZ42MYPGD35V652ZPVPYYS7A7LVXVY/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/
- https://security.gentoo.org/glsa/202104-08
- https://www.debian.org/security/2021/dsa-4906
