CVE-2021-38013: Google Chrome Buffer Overflow Vulnerability

CVE-2021-38013 Overview

CVE-2021-38013 is a heap buffer overflow vulnerability in the fingerprint recognition component of Google Chrome on ChromeOS. This flaw exists in Chrome versions prior to 96.0.4664.45 and allows a remote attacker who has already compromised a WebUI renderer process to potentially perform a sandbox escape via a crafted HTML page. The vulnerability represents a significant security risk as it enables attackers to break out of Chrome's security sandbox.

Critical Impact

A remote attacker with initial access to a compromised WebUI renderer process can leverage this heap buffer overflow to escape the browser sandbox, potentially gaining unauthorized access to the underlying ChromeOS system and sensitive user data.

Affected Products

• Google Chrome (versions prior to 96.0.4664.45)
• Google Chrome OS
• Fedora 34
• Debian Linux 10.0 and 11.0

Discovery Timeline

• 2021-12-23 - CVE-2021-38013 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-38013

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), which occurs when the software writes data past the end, or before the beginning, of the intended buffer. In this specific case, the heap buffer overflow exists within Chrome's fingerprint recognition functionality on ChromeOS devices.

The vulnerability requires an attacker to first compromise a WebUI renderer process before exploitation can occur. Once this prerequisite is met, the attacker can craft a malicious HTML page that triggers the heap buffer overflow in the fingerprint recognition component. The overflow condition allows the attacker to write arbitrary data beyond the allocated heap buffer boundaries.

The attack can be initiated remotely over the network and requires some user interaction (such as navigating to a malicious page). Successful exploitation leads to a sandbox escape, which means the attacker breaks free from Chrome's security isolation mechanisms. This changed scope characteristic makes the vulnerability particularly severe, as it allows impact to spread beyond the vulnerable component to affect the broader ChromeOS environment, potentially compromising data confidentiality, integrity, and system availability.

Root Cause

The root cause of CVE-2021-38013 is improper bounds checking in the fingerprint recognition code within Google Chrome on ChromeOS. When processing fingerprint-related data through the WebUI interface, the code fails to properly validate the size of input data before writing it to a heap-allocated buffer. This allows an attacker to provide oversized input that exceeds the buffer's capacity, resulting in adjacent heap memory being overwritten with attacker-controlled data.

Attack Vector

The attack vector for this vulnerability is network-based and requires a multi-stage approach:

1. Initial Compromise: The attacker must first compromise a WebUI renderer process through another vulnerability or attack technique
2. Payload Delivery: Once the renderer is compromised, the attacker serves a specially crafted HTML page designed to trigger the heap buffer overflow
3. Sandbox Escape: The crafted payload exploits the heap buffer overflow in the fingerprint recognition component, allowing the attacker to write beyond buffer boundaries and corrupt heap metadata or adjacent objects
4. Code Execution: By carefully controlling the overflow data, the attacker can manipulate program execution flow to escape the Chrome sandbox

The vulnerability requires user interaction in that a user must navigate to or be redirected to the attacker-controlled page while using a compromised renderer.

Detection Methods for CVE-2021-38013

Indicators of Compromise

• Unusual memory access patterns or crashes in the Chrome fingerprint recognition component
• Anomalous WebUI renderer behavior or unexpected process spawning from Chrome
• Chrome crash dumps indicating heap corruption in fingerprint-related modules
• Unexpected system calls or privilege escalation attempts originating from Chrome processes

Detection Strategies

• Monitor Chrome browser version across endpoints to identify instances running versions prior to 96.0.4664.45
• Implement endpoint detection rules to identify heap corruption signatures in Chrome processes
• Deploy memory protection solutions capable of detecting out-of-bounds write operations
• Configure security monitoring for sandbox escape indicators such as unexpected child processes from Chrome

Monitoring Recommendations

• Enable Chrome's built-in crash reporting and security logging for forensic analysis
• Implement network monitoring to detect communication patterns consistent with compromised renderer behavior
• Monitor system logs for unusual process creation events originating from Chrome browser processes
• Deploy SentinelOne Singularity to provide real-time behavioral analysis and detection of exploitation attempts

How to Mitigate CVE-2021-38013

Immediate Actions Required

• Update Google Chrome to version 96.0.4664.45 or later immediately on all ChromeOS devices
• Review and apply relevant security updates for Fedora 34 and Debian Linux 10.0/11.0 systems
• Implement network segmentation to limit potential lateral movement from compromised endpoints
• Enable Chrome's Site Isolation feature to reduce the impact of renderer compromises

Patch Information

Google has released a security patch addressing this vulnerability in Chrome version 96.0.4664.45. The fix was announced in the Google Chrome Stable Channel Update blog post. Additional tracking information is available via the Chrome Bug Tracker.

For Linux distributions:

• Fedora users should apply updates from the Fedora Package Announcement
• Debian users should reference DSA-5046 for patch details

Workarounds

• Restrict access to untrusted websites on ChromeOS devices until patches can be applied
• Implement web filtering to block known malicious domains that may attempt exploitation
• Consider disabling fingerprint authentication temporarily on unpatched ChromeOS systems
• Use SentinelOne's application control features to restrict potentially vulnerable Chrome instances

# Verify Chrome version on Linux/ChromeOS
google-chrome --version
# Expected output should show version 96.0.4664.45 or higher

# Force Chrome update check via command line (Linux)
google-chrome --check-for-update-interval=1