CVE-2021-21121
📋 TL;DR
This is a use-after-free vulnerability in the Omnibox (address bar) component of Google Chrome on Linux. It allows a remote attacker to potentially escape Chrome's sandbox and execute arbitrary code by tricking a user into visiting a malicious HTML page. Affects Chrome users on Linux systems running versions before 88.0.4324.96.
💻 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 →Edge Chromium by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise via sandbox escape leading to remote code execution with user privileges, potentially enabling lateral movement or persistence.
Likely Case
Attacker gains code execution within Chrome process, allowing data theft, browser manipulation, or further exploitation.
If Mitigated
Attack fails due to updated Chrome version or security controls preventing malicious page access.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious page) and bypassing Chrome's sandbox, but no authentication needed.
🛠️ 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. 2. Click the three-dot menu > Help > About Google Chrome. 3. Chrome will automatically check for and apply updates. 4. Restart Chrome when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript to prevent exploitation, but this breaks many websites.
chrome://settings/content/javascript > Block
Use alternative browser
linuxSwitch to an updated or unaffected browser until Chrome is patched.
🧯 If You Can't Patch
- Restrict web browsing to trusted sites only using network policies or browser extensions.
- Implement application whitelisting to block unauthorized Chrome execution.
🔍 How to Verify
Check if Vulnerable:
Check Chrome version: if on Linux and version is less than 88.0.4324.96, it is vulnerable.Check Version:
google-chrome --versionVerify Fix Applied:
Confirm Chrome version is 88.0.4324.96 or higher after update.📡 Detection & Monitoring
Log Indicators:
- Chrome crash logs with memory corruption signatures
- Unusual process spawns from Chrome
Network Indicators:
- Requests to known malicious domains hosting exploit code
SIEM Query:
source="chrome" AND (event="crash" OR process_name="chrome" AND parent_process="chrome")🔗 References
- https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.html
- https://crbug.com/1161143
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-21121
- https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop_19.html
- https://crbug.com/1161143
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-21121
