CVE-2021-4063 – This is a use-after-free vulnerability in Chrom... (How to Fix)

Q: What is the severity of CVE-2021-4063?

CVE-2021-4063 has a CVSS score of 8.8 (HIGH). This is a use-after-free vulnerability in Chrome's developer tools that allows remote attackers to potentially exploit heap corruption via a crafted HTML page. Attackers could execute arbitrary code or cause browser crashes. All users of affected Chrome versions are vulnerable when visiting malicious websites.

📋 TL;DR

This is a use-after-free vulnerability in Chrome's developer tools that allows remote attackers to potentially exploit heap corruption via a crafted HTML page. Attackers could execute arbitrary code or cause browser crashes. All users of affected Chrome versions are vulnerable when visiting malicious websites.

💻 Affected Systems

Products:

Google Chrome
Chromium-based browsers

Versions: Prior to 96.0.4664.93

Operating Systems: Windows, Linux, macOS, Android, iOS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires developer tools feature to be accessible (default enabled)

📦 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

Remote code execution leading to full system compromise, data theft, or ransomware deployment

🟠

Likely Case

Browser crash/denial of service or limited code execution in browser sandbox

🟢

If Mitigated

No impact if Chrome is updated to patched version or if developer tools are disabled

🌐 Internet-Facing: HIGH - Exploitable via visiting malicious websites

🏢 Internal Only: MEDIUM - Requires user interaction with crafted content

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Requires user to visit malicious page and interact with developer tools

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 96.0.4664.93 and later

Vendor Advisory: https://chromereleases.googleblog.com/2021/12/stable-channel-update-for-desktop.html

Restart Required: Yes

Instructions:

1. Open Chrome menu > Help > About Google Chrome 2. Chrome will automatically check for and install updates 3. Click 'Relaunch' to restart Chrome with the update

🔧 Temporary Workarounds

Disable Developer Tools

all

Prevent access to developer tools which are required for exploitation

chrome://flags/#disable-devtools
Set to 'Disabled'

Use Chrome Enterprise Policies

windows

Disable developer tools via group policy for enterprise deployments

Set 'DeveloperToolsAvailability' policy to 2 (Disallowed)

🧯 If You Can't Patch

Restrict access to untrusted websites using web filtering
Disable JavaScript execution for untrusted sites via browser extensions

🔍 How to Verify

Check if Vulnerable:

Check Chrome version in menu > Help > About Google Chrome

Check Version:

google-chrome --version (Linux) or chrome://version

Verify Fix Applied:

Confirm version is 96.0.4664.93 or higher

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports
Unexpected developer tools usage patterns

Network Indicators:

Requests to known malicious domains hosting exploit code

SIEM Query:

source="chrome" AND (event="crash" OR event="developer_tools_access")

📊 Metadata

CVE ID: CVE-2021-4063

CVSS v3 Score: 8.8 (HIGH)

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

CWE: CWE-416

Published: December 23, 2021

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2021/12/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1273176 Permissions Required
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3W46HRT2UVHWSLZB6JZHQF6JNQWKV744/
https://security.gentoo.org/glsa/202208-25 Third Party Advisory
https://www.debian.org/security/2022/dsa-5046 Third Party Advisory
https://chromereleases.googleblog.com/2021/12/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1273176 Permissions Required
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3W46HRT2UVHWSLZB6JZHQF6JNQWKV744/
https://security.gentoo.org/glsa/202208-25 Third Party Advisory
https://www.debian.org/security/2022/dsa-5046 Third Party Advisory

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