CVE-2021-30629 – This is a use-after-free vulnerability in Googl... (How to Fix)

Q: What is the severity of CVE-2021-30629?

CVE-2021-30629 has a CVSS score of 8.8 (HIGH). This is a use-after-free vulnerability in Google Chrome's permissions system 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. All Chrome users prior to version 93.0.4577.82 are affected.

📋 TL;DR

This is a use-after-free vulnerability in Google Chrome's permissions system 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. All Chrome users prior to version 93.0.4577.82 are affected.

💻 Affected Systems

Products:

Google Chrome
Chromium-based browsers

Versions: All versions prior to 93.0.4577.82

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

Default Config Vulnerable: ⚠️ Yes

Notes: All standard Chrome installations are vulnerable. Extensions or security settings don't mitigate this vulnerability.

📦 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 within the 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 page.

🏢 Internal Only: MEDIUM - Requires user to visit a malicious internal page or compromised internal site.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Requires renderer process compromise first, but then exploitation is straightforward. No public exploit code has been released.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 93.0.4577.82 and later

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

Restart Required: Yes

Instructions:

1. Open Chrome. 2. Click the three-dot menu → 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 malicious HTML pages from executing exploit code, but breaks most website functionality.

chrome://settings/content/javascript → Block

Use Chrome Enterprise policies

all

Enforce automatic updates via Group Policy or MDM to ensure patching.

Google Chrome Enterprise documentation for update policies

🧯 If You Can't Patch

Use alternative browsers until Chrome can be updated.
Implement network filtering to block known malicious websites and restrict internet browsing.

🔍 How to Verify

Check if Vulnerable:

Check Chrome version: If version is less than 93.0.4577.82, system is vulnerable.

Check Version:

chrome://version/ or 'google-chrome --version' (Linux) or check About Google Chrome

Verify Fix Applied:

Confirm Chrome version is 93.0.4577.82 or higher after update.

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports with memory corruption signatures
Unexpected renderer process terminations

Network Indicators:

Requests to known malicious domains hosting exploit code
Unusual outbound connections after visiting suspicious sites

SIEM Query:

source="chrome" AND (event="crash" OR event="renderer_killed") AND version<93.0.4577.82

📊 Metadata

CVE ID: CVE-2021-30629

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.html Release Notes,Vendor Advisory
https://crbug.com/1243646 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://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop.html Release Notes,Vendor Advisory
https://crbug.com/1243646 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/

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