CVE-2020-6539 – This is a use-after-free vulnerability in Chrom... (How to Fix)

Q: What is the severity of CVE-2020-6539?

CVE-2020-6539 has a CVSS score of 8.8 (HIGH). This is a use-after-free vulnerability in Chrome's CSS engine 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 CSS engine 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: All versions prior to 84.0.4147.105

Operating Systems: Windows, macOS, Linux, Android, Chrome OS

Default Config Vulnerable: ⚠️ Yes

Notes: All default Chrome configurations are vulnerable. Affects both desktop and mobile versions.

📦 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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Debian Linux by Debian

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Fedora by Fedoraproject

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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 within browser sandbox.

🟢

If Mitigated

No impact if Chrome is fully patched or if exploit attempts are blocked by security controls.

🌐 Internet-Facing: HIGH - Attackers can exploit via malicious websites without user interaction beyond visiting the site.

🏢 Internal Only: MEDIUM - Risk exists if internal users visit compromised internal sites or if attackers gain internal network access.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploit requires user to visit malicious website. No authentication needed. Public bug report includes technical details.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 84.0.4147.105 and later

Vendor Advisory: https://chromereleases.googleblog.com/2020/07/stable-channel-update-for-desktop_27.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 updates. 4. Click 'Relaunch' to restart Chrome with the update.

🔧 Temporary Workarounds

Disable JavaScript

all

Prevents exploitation by disabling JavaScript execution, but breaks most websites.

chrome://settings/content/javascript → Block

Use site isolation

all

Enables site isolation to limit impact of successful exploitation.

chrome://flags/#enable-site-per-process → Enable

🧯 If You Can't Patch

Use alternative browser until Chrome can be updated
Implement web filtering to block known malicious sites

🔍 How to Verify

Check if Vulnerable:

Check Chrome version: chrome://version/ and verify version is below 84.0.4147.105

Check Version:

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

Verify Fix Applied:

Confirm Chrome version is 84.0.4147.105 or higher via chrome://version/

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports
Unexpected browser termination events
Security event logs showing exploit attempts

Network Indicators:

Requests to known exploit hosting domains
Unusual outbound connections from Chrome processes

SIEM Query:

source="chrome" AND (event_type="crash" OR message="*heap corruption*" OR message="*use-after-free*")

📊 Metadata

CVE ID: CVE-2020-6539

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: September 21, 2020

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2020/07/stable-channel-update-for-desktop_27.html Release Notes,Vendor Advisory
https://crbug.com/1105635 Permissions Required,Vendor 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/2020/07/stable-channel-update-for-desktop_27.html Release Notes,Vendor Advisory
https://crbug.com/1105635 Permissions Required,Vendor 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

📤 Share & Export

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🔗 Related Vulnerabilities

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