CVE-2021-37956 – This is a use-after-free vulnerability in Googl... (How to Fix)

Q: What is the severity of CVE-2021-37956?

CVE-2021-37956 has a CVSS score of 8.8 (HIGH). This is a use-after-free vulnerability in Google Chrome for Android that allows a remote attacker who has already compromised the renderer process to potentially exploit heap corruption. Attackers could execute arbitrary code or cause crashes by tricking users into visiting a malicious HTML page. Users of Google Chrome on Android prior to version 94.0.4606.54 are affected.

📋 TL;DR

This is a use-after-free vulnerability in Google Chrome for Android that allows a remote attacker who has already compromised the renderer process to potentially exploit heap corruption. Attackers could execute arbitrary code or cause crashes by tricking users into visiting a malicious HTML page. Users of Google Chrome on Android prior to version 94.0.4606.54 are affected.

💻 Affected Systems

Products:

Google Chrome for Android

Versions: Versions prior to 94.0.4606.54

Operating Systems: Android

Default Config Vulnerable: ⚠️ Yes

Notes: Requires renderer process compromise as a prerequisite, typically through another vulnerability or social engineering.

📦 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

Remote code execution leading to full device compromise, data theft, or installation of persistent malware.

🟠

Likely Case

Application crash (denial of service) or limited code execution within the sandboxed renderer process.

🟢

If Mitigated

No impact if Chrome is updated to patched version or if exploit attempts are blocked by security controls.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires chaining with another vulnerability to compromise the renderer process first, then triggering the use-after-free condition.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 94.0.4606.54

Vendor Advisory: https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_21.html

Restart Required: Yes

Instructions:

1. Open Google Play Store on Android device. 2. Search for 'Google Chrome'. 3. If update is available, tap 'Update'. 4. Restart Chrome after update completes.

🔧 Temporary Workarounds

Disable Offline Mode

android

Prevents exploitation by disabling the vulnerable offline use functionality.

chrome://flags/#offline-pages-enabled
Set to 'Disabled'

🧯 If You Can't Patch

Restrict access to untrusted websites using web filtering or proxy controls.
Implement application allowlisting to prevent unauthorized Chrome usage.

🔍 How to Verify

Check if Vulnerable:

Check Chrome version in Settings > About Chrome. If version is below 94.0.4606.54, device is vulnerable.

Check Version:

chrome://version/

Verify Fix Applied:

Confirm Chrome version is 94.0.4606.54 or higher in Settings > About Chrome.

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports with memory corruption signatures
Unexpected renderer process terminations

Network Indicators:

Requests to known malicious domains hosting exploit HTML
Unusual traffic patterns from Chrome processes

SIEM Query:

source="chrome_crash_reports" AND (event_type="crash" OR event_type="memory_corruption")

📊 Metadata

CVE ID: CVE-2021-37956

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: October 8, 2021

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_21.html Release Notes,Vendor Advisory
https://crbug.com/1243117 Permissions Required,Vendor Advisory
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 Third Party Advisory
https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_21.html Release Notes,Vendor Advisory
https://crbug.com/1243117 Permissions Required,Vendor Advisory
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 Third Party Advisory

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