CVE-2021-4057 – This is a use-after-free vulnerability in Chrom... (How to Fix)

Q: What is the severity of CVE-2021-4057?

CVE-2021-4057 has a CVSS score of 8.8 (HIGH). This is a use-after-free vulnerability in Chrome's file API that allows a remote attacker who has already compromised the renderer process to potentially exploit heap corruption. Attackers could execute arbitrary code or cause browser crashes by tricking users into visiting a malicious webpage. All Chrome users prior to version 96.0.4664.93 are affected.

📋 TL;DR

This is a use-after-free vulnerability in Chrome's file API that allows a remote attacker who has already compromised the renderer process to potentially exploit heap corruption. Attackers could execute arbitrary code or cause browser crashes by tricking users into visiting a malicious webpage. All Chrome users prior to version 96.0.4664.93 are affected.

💻 Affected Systems

Products:

Google Chrome
Chromium-based browsers

Versions: All versions prior to 96.0.4664.93

Operating Systems: Windows, Linux, macOS, Android

Default Config Vulnerable: ⚠️ Yes

Notes: Requires renderer process compromise first, often through another vulnerability chain

📦 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 system compromise, data theft, or ransomware deployment

🟠

Likely Case

Browser crash/denial of service, potential sandbox escape leading to limited code execution

🟢

If Mitigated

Browser crash only, with proper sandboxing preventing system compromise

🌐 Internet-Facing: HIGH - Exploitable via malicious web content without user interaction beyond visiting a page

🏢 Internal Only: MEDIUM - Requires initial renderer compromise but could be chained with other vulnerabilities

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Public exploit details available on Packet Storm, requires chaining with renderer compromise

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 96.0.4664.93 and later

Vendor Advisory: https://chromereleases.googleblog.com/2021/12/stable-channel-update-for-desktop.html

Restart Required: Yes

Instructions:

1. Open Chrome menu > Help > About Google Chrome 2. Allow browser to check for updates 3. Restart Chrome when prompted 4. Verify version is 96.0.4664.93 or higher

🔧 Temporary Workarounds

Disable JavaScript

all

Prevents exploitation by disabling JavaScript execution

chrome://settings/content/javascript > Block

Use Site Isolation

all

Enhances sandboxing between sites

chrome://flags/#site-isolation-trial-opt-out > Disabled

🧯 If You Can't Patch

Deploy network filtering to block known malicious domains
Implement application whitelisting to prevent unauthorized Chrome execution

🔍 How to Verify

Check if Vulnerable:

Check Chrome version via chrome://version and compare to 96.0.4664.93

Check Version:

google-chrome --version (Linux) or open chrome://version

Verify Fix Applied:

Confirm Chrome version is 96.0.4664.93 or higher and test with known exploit PoC

📡 Detection & Monitoring

Log Indicators:

Chrome crash reports with memory corruption signatures
Unusual renderer process behavior

Network Indicators:

Connections to domains hosting exploit code
Unusual outbound traffic post-exploit

SIEM Query:

source="chrome_crash_reports" AND (message="heap corruption" OR message="use-after-free")

📊 Metadata

CVE ID: CVE-2021-4057

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: December 23, 2021

Last Updated: November 21, 2024

🔗 References

http://packetstormsecurity.com/files/165486/Chrome-storage-BlobURLStoreImpl-Revoke-Heap-Use-After-Free.html Third Party Advisory,VDB Entry
https://chromereleases.googleblog.com/2021/12/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1262183 Permissions Required
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3W46HRT2UVHWSLZB6JZHQF6JNQWKV744/
https://security.gentoo.org/glsa/202208-25 Third Party Advisory
https://www.debian.org/security/2022/dsa-5046 Third Party Advisory
http://packetstormsecurity.com/files/165486/Chrome-storage-BlobURLStoreImpl-Revoke-Heap-Use-After-Free.html Third Party Advisory,VDB Entry
https://chromereleases.googleblog.com/2021/12/stable-channel-update-for-desktop.html Vendor Advisory
https://crbug.com/1262183 Permissions Required
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3W46HRT2UVHWSLZB6JZHQF6JNQWKV744/
https://security.gentoo.org/glsa/202208-25 Third Party Advisory
https://www.debian.org/security/2022/dsa-5046 Third Party Advisory

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