CVE-2021-38017 – This vulnerability allows attackers to bypass i... (How to Fix)

Q: What is the severity of CVE-2021-38017?

CVE-2021-38017 has a CVSS score of 8.8 (HIGH). This vulnerability allows attackers to bypass iframe sandbox navigation restrictions in Google Chrome, potentially enabling malicious websites to perform unauthorized actions. It affects users running Chrome versions before 96.0.4664.45. The issue stems from insufficient policy enforcement in Chrome's iframe sandbox implementation.

📋 TL;DR

This vulnerability allows attackers to bypass iframe sandbox navigation restrictions in Google Chrome, potentially enabling malicious websites to perform unauthorized actions. It affects users running Chrome versions before 96.0.4664.45. The issue stems from insufficient policy enforcement in Chrome's iframe sandbox implementation.

💻 Affected Systems

Products:

Google Chrome

Versions: All versions prior to 96.0.4664.45

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

Default Config Vulnerable: ⚠️ Yes

Notes: All Chrome-based browsers (Chromium, Edge, etc.) may be affected if using vulnerable Chromium 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...

Learn more about Chrome →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete sandbox escape allowing arbitrary code execution, data theft, or system compromise through malicious web content.

🟠

Likely Case

Limited sandbox bypass enabling unauthorized navigation, content injection, or cross-origin data access within browser context.

🟢

If Mitigated

Minimal impact with proper browser updates and security controls in place.

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

🏢 Internal Only: MEDIUM - Requires user to visit malicious internal pages, but could be used in phishing campaigns.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires crafting malicious HTML pages but no authentication or special privileges needed.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 96.0.4664.45 and later

Vendor Advisory: https://chromereleases.googleblog.com/2021/11/stable-channel-update-for-desktop.html

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Disable JavaScript in iframes

all

Configure Content Security Policy to restrict iframe JavaScript execution

Content-Security-Policy: sandbox allow-same-origin;

Use browser extensions to block iframes

all

Install extensions that block or control iframe loading

🧯 If You Can't Patch

Implement network filtering to block known malicious domains
Use application allowlisting to restrict browser usage to trusted sites only

🔍 How to Verify

Check if Vulnerable:

Check Chrome version: chrome://version/ and verify if version is below 96.0.4664.45

Check Version:

chrome://version/

Verify Fix Applied:

Confirm Chrome version is 96.0.4664.45 or higher via chrome://version/

📡 Detection & Monitoring

Log Indicators:

Unusual iframe navigation patterns
Sandbox policy violation attempts in browser logs

Network Indicators:

Requests from iframes to unexpected domains
Multiple rapid navigation attempts from single pages

SIEM Query:

source="browser_logs" AND (event="sandbox_violation" OR event="iframe_navigation")

📊 Metadata

CVE ID: CVE-2021-38017

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-863

Published: December 23, 2021

Last Updated: November 21, 2024

🔗 References

https://chromereleases.googleblog.com/2021/11/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1256822 Permissions Required
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3W46HRT2UVHWSLZB6JZHQF6JNQWKV744/
https://www.debian.org/security/2022/dsa-5046 Third Party Advisory
https://chromereleases.googleblog.com/2021/11/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1256822 Permissions Required
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3W46HRT2UVHWSLZB6JZHQF6JNQWKV744/
https://www.debian.org/security/2022/dsa-5046 Third Party Advisory

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