CVE-2021-37973
📋 TL;DR
This is a use-after-free vulnerability in Google Chrome's Portals feature that allows a remote attacker who has already compromised the renderer process to potentially escape the browser sandbox. It affects Chrome versions prior to 94.0.4606.61. Users running vulnerable Chrome versions are at risk.
💻 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 sandbox escape leading to arbitrary code execution with the privileges of the Chrome process, potentially allowing installation of malware, data theft, or system takeover.
Likely Case
Limited impact requiring prior renderer compromise, but successful exploitation could lead to sandbox escape and elevated privileges on the affected system.
If Mitigated
Minimal impact if Chrome is fully patched, sandboxing is properly configured, and users don't visit malicious sites.
🎯 Exploit Status
Exploitation requires prior renderer process compromise and knowledge of the Portals feature.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 94.0.4606.61 and later
Vendor Advisory: https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_24.html
Restart Required: Yes
Instructions:
1. Open Chrome. 2. Click the three-dot menu. 3. Go to Help > About Google Chrome. 4. Chrome will automatically check for and install updates. 5. Restart Chrome when prompted.
🔧 Temporary Workarounds
Disable Portals feature
allDisable the experimental Portals feature in Chrome flags
Navigate to chrome://flags/#enable-portals and set to Disabled
🧯 If You Can't Patch
- Disable JavaScript in Chrome settings
- Use alternative browser until patching is possible
🔍 How to Verify
Check if Vulnerable:
Check Chrome version via chrome://version and compare to 94.0.4606.61Check Version:
google-chrome --version (Linux) or navigate to chrome://versionVerify Fix Applied:
Verify Chrome version is 94.0.4606.61 or higher📡 Detection & Monitoring
Log Indicators:
- Chrome crash reports
- Unexpected renderer process termination
- Sandbox violation logs
Network Indicators:
- Requests to known malicious domains hosting exploit code
SIEM Query:
source="chrome" AND (event_type="crash" OR message="renderer")🔗 References
- https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_24.html
- https://crbug.com/1251727
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4DDW7HAHTS3SDVXBQUY4SURELO5D4X7R/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PM7MOYYHJSWLIFZ4TPJTD7MSA3HSSLV2/
- https://www.debian.org/security/2022/dsa-5046
- https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_24.html
- https://crbug.com/1251727
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4DDW7HAHTS3SDVXBQUY4SURELO5D4X7R/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PM7MOYYHJSWLIFZ4TPJTD7MSA3HSSLV2/
- https://www.debian.org/security/2022/dsa-5046
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-37973
