CVE-2020-6554 – This is a use-after-free vulnerability in Chrom... (How to Fix)

Q: What is the severity of CVE-2020-6554?

CVE-2020-6554 has a CVSS score of 8.6 (HIGH). This is a use-after-free vulnerability in Chrome's extension system that allows a remote attacker to escape Chrome's sandbox via a malicious extension. It affects all Chrome users running versions before 84.0.4147.125. Successful exploitation could lead to arbitrary code execution on the host system.

📋 TL;DR

This is a use-after-free vulnerability in Chrome's extension system that allows a remote attacker to escape Chrome's sandbox via a malicious extension. It affects all Chrome users running versions before 84.0.4147.125. Successful exploitation could lead to arbitrary code execution on the host system.

💻 Affected Systems

Products:

Google Chrome
Chromium-based browsers

Versions: All versions prior to 84.0.4147.125

Operating Systems: Windows, macOS, Linux, Chrome OS

Default Config Vulnerable: ⚠️ Yes

Notes: Vulnerability is in Chrome's extension subsystem and affects all default configurations. Requires user to install or be tricked into installing a malicious extension.

📦 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

Complete system compromise via sandbox escape leading to arbitrary code execution with user privileges, potentially enabling persistence, data theft, and lateral movement.

🟠

Likely Case

Local privilege escalation allowing malicious extensions to break out of Chrome's security sandbox and execute code on the host operating system.

🟢

If Mitigated

No impact if Chrome is fully patched or if extension installation is restricted to trusted sources only.

🌐 Internet-Facing: HIGH - Attackers can host malicious extensions on websites or distribute them through various channels to target users.

🏢 Internal Only: MEDIUM - Risk exists if users install untrusted extensions internally, but requires user interaction or policy bypass.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploit requires user to install a malicious extension. The bug report (crbug.com/1094235) contains technical details that could aid exploitation. Sandbox escape vulnerabilities are highly valuable to attackers.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 84.0.4147.125 and later

Vendor Advisory: https://chromereleases.googleblog.com/2020/08/stable-channel-update-for-desktop.html

Restart Required: Yes

Instructions:

1. Open Chrome and click the three-dot menu > Help > About Google Chrome. 2. Chrome will automatically check for updates and install version 84.0.4147.125 or later. 3. Click 'Relaunch' to restart Chrome with the fix applied.

🔧 Temporary Workarounds

Disable extension installation

all

Prevent users from installing new extensions to block the attack vector

For enterprise: Use Chrome policies to restrict extension installation via Group Policy or MDM

Restrict extension sources

all

Only allow extensions from Chrome Web Store

chrome://settings > Extensions > Check 'Allow from Chrome Web Store only'

🧯 If You Can't Patch

Implement application whitelisting to block Chrome execution entirely
Use network filtering to block access to untrusted extension sources and update servers

🔍 How to Verify

Check if Vulnerable:

Check Chrome version: If version is less than 84.0.4147.125, system is vulnerable.

Check Version:

On Chrome: chrome://version/ or Command Line: google-chrome --version

Verify Fix Applied:

Confirm Chrome version is 84.0.4147.125 or higher after update.

📡 Detection & Monitoring

Log Indicators:

Unusual extension installation events
Chrome crash reports with extension-related memory errors
Process creation from Chrome with unusual parent-child relationships

Network Indicators:

Downloads of .crx files from untrusted sources
Chrome extension update requests to non-Google domains

SIEM Query:

source="chrome_extension_logs" AND (event="install" OR event="update") AND extension_id NOT IN [approved_list]

📊 Metadata

CVE ID: CVE-2020-6554

CVSS v3 Score: 8.6 (HIGH)

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

CWE: CWE-416

Published: September 21, 2020

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2020/08/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1094235 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EE7XWIZBME7JAY7N6CGPET4CLNHHEIVT/
https://www.debian.org/security/2021/dsa-4824 Third Party Advisory
https://chromereleases.googleblog.com/2020/08/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1094235 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EE7XWIZBME7JAY7N6CGPET4CLNHHEIVT/
https://www.debian.org/security/2021/dsa-4824 Third Party Advisory

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🔗 Related Vulnerabilities

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