CVE-2021-21110 – This is a use-after-free vulnerability in Googl... (How to Fix)

Q: What is the severity of CVE-2021-21110?

CVE-2021-21110 has a CVSS score of 9.6 (CRITICAL). This is a use-after-free vulnerability in Google Chrome's safe browsing component that allows a remote attacker to potentially escape the browser sandbox via a crafted HTML page. It affects Chrome users on all platforms running versions prior to 87.0.4280.141. Successful exploitation could lead to arbitrary code execution with the privileges of the Chrome process.

📋 TL;DR

This is a use-after-free vulnerability in Google Chrome's safe browsing component that allows a remote attacker to potentially escape the browser sandbox via a crafted HTML page. It affects Chrome users on all platforms running versions prior to 87.0.4280.141. Successful exploitation could lead to arbitrary code execution with the privileges of the Chrome process.

💻 Affected Systems

Products:

Google Chrome
Chromium-based browsers

Versions: All versions prior to 87.0.4280.141

Operating Systems: Windows, Linux, macOS, Chrome OS

Default Config Vulnerable: ⚠️ Yes

Notes: All standard Chrome installations are vulnerable. Safe browsing feature is enabled by default.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise via sandbox escape leading to arbitrary code execution with user privileges, potentially enabling further privilege escalation.

🟠

Likely Case

Remote code execution within the Chrome process context, allowing data theft, malware installation, or persistence mechanisms.

🟢

If Mitigated

Limited impact if Chrome sandbox remains intact, potentially only browser crash or denial of service.

🌐 Internet-Facing: HIGH - Attackers can exploit via malicious websites or ads without user interaction beyond visiting a page.

🏢 Internal Only: MEDIUM - Requires user to visit a malicious internal page, but could be combined with phishing or other internal attacks.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires bypassing Chrome's security mitigations but has been actively exploited according to Google's disclosure.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 87.0.4280.141 and later

Vendor Advisory: https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop.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 and install updates. 4. Click 'Relaunch' to restart Chrome with the updated version.

🔧 Temporary Workarounds

Disable JavaScript

all

Temporarily disable JavaScript to prevent exploitation via malicious scripts

chrome://settings/content/javascript

Use alternative browser

all

Switch to a non-Chromium browser until patched

🧯 If You Can't Patch

Implement network filtering to block known malicious domains and restrict web browsing
Enable enhanced security features like site isolation and strict origin isolation in Chrome flags

🔍 How to Verify

Check if Vulnerable:

Check Chrome version via chrome://version and compare to 87.0.4280.141

Check Version:

chrome://version or 'google-chrome --version' on Linux

Verify Fix Applied:

Confirm Chrome version is 87.0.4280.141 or higher after update

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports with safe browsing component
Unexpected Chrome process termination
Security event logs showing sandbox violations

Network Indicators:

Unusual outbound connections from Chrome processes
Traffic to known exploit domains

SIEM Query:

process_name:"chrome.exe" AND (event_id:1000 OR event_id:1001) AND description:"safe_browsing"

📊 Metadata

CVE ID: CVE-2021-21110

CVSS v3 Score: 9.6 (CRITICAL)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

CWE: CWE-416

Published: January 8, 2021

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop.html Release Notes,Vendor Advisory
https://crbug.com/1152451 Permissions Required,Vendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VVUWIJKZTZTG6G475OR6PP4WPQBVM6PS/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z6P6AVVFP7B2M4H7TJQBASRZIBLOTUFN/
https://security.gentoo.org/glsa/202101-05 Third Party Advisory
https://www.debian.org/security/2021/dsa-4832 Third Party Advisory
https://chromereleases.googleblog.com/2021/01/stable-channel-update-for-desktop.html Release Notes,Vendor Advisory
https://crbug.com/1152451 Permissions Required,Vendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VVUWIJKZTZTG6G475OR6PP4WPQBVM6PS/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z6P6AVVFP7B2M4H7TJQBASRZIBLOTUFN/
https://security.gentoo.org/glsa/202101-05 Third Party Advisory
https://www.debian.org/security/2021/dsa-4832 Third Party Advisory

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