CVE-2021-21226
📋 TL;DR
This is a use-after-free vulnerability in Google Chrome's navigation component that allows a compromised renderer process to escape the browser sandbox. Attackers can exploit this via a crafted HTML page to execute arbitrary code with elevated privileges. All Chrome users prior to version 90.0.4430.85 are affected.
💻 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...
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⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise where an attacker gains full control of the victim's computer, installs malware, steals sensitive data, and uses the system for further attacks.
Likely Case
Remote code execution leading to data theft, ransomware deployment, or system takeover, especially when combined with other vulnerabilities.
If Mitigated
Limited impact if Chrome sandbox is properly configured and other security controls are in place, potentially containing the exploit to the browser process.
🎯 Exploit Status
Exploitation requires chaining with another vulnerability to compromise the renderer process first. The sandbox escape component is sophisticated but has been weaponized in similar Chrome vulnerabilities.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 90.0.4430.85
Vendor Advisory: https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop_20.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 90.0.4430.85 or later. 4. Click 'Relaunch' to restart Chrome with the update.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript to prevent exploitation via crafted HTML pages
chrome://settings/content/javascript
Use Site Isolation
allEnsure site isolation is enabled to limit impact of renderer compromise
chrome://flags/#site-isolation-trial-opt-out (set to Disabled)
🧯 If You Can't Patch
- Disable Chrome entirely and use an alternative browser that is patched
- Implement network filtering to block malicious websites and restrict Chrome usage to trusted sites only
🔍 How to Verify
Check if Vulnerable:
Check Chrome version by navigating to chrome://version and verifying version is below 90.0.4430.85Check Version:
google-chrome --version (Linux/Mac) or navigate to chrome://version (all platforms)Verify Fix Applied:
Confirm Chrome version is 90.0.4430.85 or higher via chrome://version📡 Detection & Monitoring
Log Indicators:
- Chrome crash reports with navigation-related errors
- Unexpected Chrome process termination or restart patterns
- Security event logs showing Chrome accessing privileged system resources
Network Indicators:
- Unusual outbound connections from Chrome processes to known malicious domains
- HTTP requests to pages with suspicious navigation parameters
SIEM Query:
source="chrome_logs" AND (event_type="crash" OR process_name="chrome.exe") AND message="*navigation*" OR "*use-after-free*"🔗 References
- https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop_20.html
- https://crbug.com/1197904
- 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_20.html
- https://crbug.com/1197904
- 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
