CVE-2021-30550
📋 TL;DR
This is a use-after-free vulnerability in Chrome's Accessibility component that allows heap corruption. Attackers can exploit it by tricking users into installing a malicious extension and visiting a crafted HTML page. All Chrome users prior to version 91.0.4472.101 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
Full system compromise via arbitrary code execution, potentially leading to data theft, ransomware deployment, or complete system takeover.
Likely Case
Browser compromise allowing session hijacking, credential theft, and installation of additional malware through the exploited browser context.
If Mitigated
Limited impact with proper extension vetting and user awareness, potentially only browser crash or denial of service.
🎯 Exploit Status
Exploitation requires social engineering to install malicious extension and visit crafted page. No public exploit code available at disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 91.0.4472.101
Vendor Advisory: https://chromereleases.googleblog.com/2021/06/stable-channel-update-for-desktop.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 update 4. Click 'Relaunch' to restart Chrome with the patched version
🔧 Temporary Workarounds
Disable Extension Installation
allPrevent users from installing extensions to block the initial attack vector
For enterprise: Use Group Policy to disable extension installation
For individuals: Avoid installing extensions from untrusted sources
Enable Enhanced Protection
allEnable Chrome's Enhanced Protection mode for additional security features
Settings → Privacy and security → Security → Enhanced protection
🧯 If You Can't Patch
- Restrict extension installation to Chrome Web Store only and block sideloading
- Implement network filtering to block access to suspicious or untrusted websites
🔍 How to Verify
Check if Vulnerable:
Check Chrome version in Settings → About Chrome. If version is below 91.0.4472.101, system is vulnerable.Check Version:
chrome://version/ or 'google-chrome --version' on Linux/macOS terminalVerify Fix Applied:
Confirm Chrome version is 91.0.4472.101 or higher in Settings → About Chrome.📡 Detection & Monitoring
Log Indicators:
- Chrome crash reports with accessibility-related stack traces
- Unexpected extension installation events
- Accessibility service errors in system logs
Network Indicators:
- Requests to known malicious domains hosting crafted HTML pages
- Unusual extension update traffic from non-Chrome Web Store sources
SIEM Query:
source="chrome" AND (event="crash" OR event="extension_install") AND version<"91.0.4472.101"🔗 References
- https://chromereleases.googleblog.com/2021/06/stable-channel-update-for-desktop.html
- https://crbug.com/1212500
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ETMZL6IHCTCTREEL434BQ4THQ7EOHJ43/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PAT6EOXVQFE6JFMFQF4IKAOUQSHMHL54/
- https://security.gentoo.org/glsa/202107-06
- https://chromereleases.googleblog.com/2021/06/stable-channel-update-for-desktop.html
- https://crbug.com/1212500
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ETMZL6IHCTCTREEL434BQ4THQ7EOHJ43/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PAT6EOXVQFE6JFMFQF4IKAOUQSHMHL54/
- https://security.gentoo.org/glsa/202107-06
