CVE-2021-30526 – This vulnerability allows an attacker to perfor... (How to Fix)

Q: What is the severity of CVE-2021-30526?

CVE-2021-30526 has a CVSS score of 8.8 (HIGH). This vulnerability allows an attacker to perform out-of-bounds memory writes in Google Chrome's TabStrip component by convincing a user to install a malicious extension and visit a crafted HTML page. This could lead to arbitrary code execution, data corruption, or browser crashes. All users running vulnerable versions of Google Chrome are affected.

📋 TL;DR

This vulnerability allows an attacker to perform out-of-bounds memory writes in Google Chrome's TabStrip component by convincing a user to install a malicious extension and visit a crafted HTML page. This could lead to arbitrary code execution, data corruption, or browser crashes. All users running vulnerable versions of Google Chrome are affected.

💻 Affected Systems

Products:

Google Chrome

Versions: All versions prior to 91.0.4472.77

Operating Systems: Windows, Linux, macOS, Chrome OS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires user to install a malicious extension, but extensions can be installed from sources other than Chrome Web Store. All default Chrome configurations are vulnerable.

📦 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 with the privileges of the Chrome process, potentially leading to full system compromise, data theft, or installation of persistent malware.

🟠

Likely Case

Browser crash (denial of service) or limited memory corruption leading to unstable browser behavior, though code execution is possible with sophisticated exploitation.

🟢

If Mitigated

No impact if Chrome is updated to patched version or if malicious extension installation is prevented through security controls.

🌐 Internet-Facing: HIGH - Attack can be triggered via malicious web content, making internet-facing systems vulnerable to drive-by attacks.

🏢 Internal Only: MEDIUM - Internal users could be targeted via phishing or compromised internal websites, but requires user interaction.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires convincing user to install malicious extension AND visit crafted HTML page. No public exploit code has been identified in references.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 91.0.4472.77

Vendor Advisory: https://chromereleases.googleblog.com/2021/05/stable-channel-update-for-desktop_25.html

Restart Required: Yes

Instructions:

1. Open Chrome browser. 2. Click the three-dot menu → Help → About Google Chrome. 3. Chrome will automatically check for updates and install version 91.0.4472.77 or later. 4. Click 'Relaunch' to restart Chrome with the update.

🔧 Temporary Workarounds

Disable Extension Installation

all

Prevent users from installing extensions to block the attack vector.

For enterprise: Use Chrome Enterprise policies to disable extension installation via Group Policy or MDM.

Restrict Extension Sources

all

Only allow extensions from Chrome Web Store.

Set ExtensionInstallSources policy to only allow https://chrome.google.com/webstore/*

🧯 If You Can't Patch

Implement application whitelisting to prevent execution of malicious code if exploitation occurs.
Use network segmentation to limit potential lateral movement from compromised browsers.

🔍 How to Verify

Check if Vulnerable:

Check Chrome version: If version is less than 91.0.4472.77, system is vulnerable.

Check Version:

On Windows/Linux/macOS: chrome://version/ or 'google-chrome --version' in terminal

Verify Fix Applied:

Confirm Chrome version is 91.0.4472.77 or higher after update.

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports with memory access violation errors
Unexpected extension installation events in Chrome logs

Network Indicators:

Downloads of suspicious Chrome extensions from non-Google sources
HTTP requests to known malicious domains hosting crafted HTML pages

SIEM Query:

source="chrome_logs" AND (event="crash" AND error="access_violation") OR (event="extension_install" AND source!="chrome_web_store")

📊 Metadata

CVE ID: CVE-2021-30526

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-787

Published: June 7, 2021

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2021/05/stable-channel-update-for-desktop_25.html Release Notes,Vendor Advisory
https://crbug.com/1198717 Exploit,Issue Tracking,Patch,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ETMZL6IHCTCTREEL434BQ4THQ7EOHJ43/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PAT6EOXVQFE6JFMFQF4IKAOUQSHMHL54/
https://security.gentoo.org/glsa/202107-06 Third Party Advisory
https://chromereleases.googleblog.com/2021/05/stable-channel-update-for-desktop_25.html Release Notes,Vendor Advisory
https://crbug.com/1198717 Exploit,Issue Tracking,Patch,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ETMZL6IHCTCTREEL434BQ4THQ7EOHJ43/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PAT6EOXVQFE6JFMFQF4IKAOUQSHMHL54/
https://security.gentoo.org/glsa/202107-06 Third Party Advisory

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