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 prior to version 96.0.4664.45. The flaw allows a remote attacker who has already compromised a WebUI renderer process to potentially escape the Chrome sandbox using a crafted HTML page. The vulnerability is tracked under CWE-787 (Out-of-bounds Write) and affects Google Chrome, ChromeOS, Fedora, and Debian Linux distributions that ship Chromium-based packages.

Critical Impact

Successful exploitation enables sandbox escape from a compromised renderer process, granting an attacker access to ChromeOS components running outside the browser sandbox.

Affected Products

• Google Chrome prior to 96.0.4664.45
• Google ChromeOS prior to 96.0.4664.45
• Fedora 34 (Chromium package) and 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

The vulnerability resides in the fingerprint recognition functionality shipped with Chrome on ChromeOS. A heap buffer overflow occurs when input data is written past the bounds of a heap-allocated buffer used by the fingerprint subsystem. Because the affected code path is reachable from a WebUI renderer, an attacker who already controls that renderer can drive the overflow through a crafted HTML page.

The exploit chain assumes prior compromise of a WebUI renderer process. WebUI pages in Chrome run with elevated privileges compared to standard web content. By corrupting heap metadata or adjacent objects in a higher-privilege process, an attacker can pivot toward a sandbox escape and gain access to resources outside the renderer sandbox.

Root Cause

The root cause is an out-of-bounds write [CWE-787] in the ChromeOS fingerprint recognition handling code. The implementation does not adequately validate the size of data being copied into a heap buffer, allowing controlled bytes to overwrite adjacent memory. Memory corruption of this class is the most common bug category exploited for browser sandbox escapes.

Attack Vector

The attack vector is network-based with user interaction required. The attacker must first compromise a WebUI renderer process, typically by chaining a separate renderer-level bug. Once inside the renderer, the attacker delivers a crafted HTML page that triggers the fingerprint recognition code path with attacker-controlled data, producing the heap overflow and enabling a sandbox escape.

No public proof-of-concept exploit is associated with this CVE. Technical details remain restricted in Chromium Bug Report #1242392 per Google's standard policy of withholding bug details until users have updated.

Detection Methods for CVE-2021-38013

Indicators of Compromise

• Chrome or Chromium browser processes on ChromeOS, Fedora, or Debian endpoints running versions below 96.0.4664.45.
• Unexpected child processes spawned by the Chrome renderer or browser process, particularly processes interacting with biometric or fingerprint device endpoints.
• Renderer process crashes referencing fingerprint or WebUI components in Chrome crash logs.

Detection Strategies

• Inventory installed Chrome and Chromium versions across the fleet and flag any instance below 96.0.4664.45.
• Monitor for anomalous renderer-to-browser IPC patterns and unexpected access to ChromeOS biometric services from sandboxed processes.
• Correlate browser crash telemetry with subsequent privilege-sensitive activity on the same host within a short time window.

Monitoring Recommendations

• Centralize Chrome version telemetry and patch compliance reporting through endpoint management tooling.
• Ingest browser crash dumps and EDR process telemetry into a SIEM to identify exploitation attempts that produce renderer instability.
• Alert on Chrome processes that suddenly perform actions inconsistent with normal browsing, such as spawning shells or accessing system binaries.

How to Mitigate CVE-2021-38013

Immediate Actions Required

• Update Google Chrome and ChromeOS to version 96.0.4664.45 or later on all affected endpoints.
• Apply distribution-specific Chromium updates referenced in the Debian Security Advisory DSA-5046 and the Fedora Package Announcement.
• Enforce browser auto-update policies through enterprise management consoles to prevent version drift.

Patch Information

Google addressed this vulnerability in the Chrome stable channel update documented in the Google Chrome Update Announcement. The fix is available in Chrome 96.0.4664.45 and corresponding ChromeOS releases. Downstream Linux distributions shipped patched Chromium packages through their respective security advisories.

Workarounds

• No supported workaround exists other than upgrading to the patched version.
• Restrict use of ChromeOS fingerprint authentication features until affected devices are confirmed patched.
• Limit user exposure to untrusted web content on unpatched endpoints by enforcing browsing restrictions through endpoint policy.

# Verify the installed Chrome version on Linux endpoints
google-chrome --version

# Force a Chrome update on Debian/Ubuntu
sudo apt-get update && sudo apt-get install --only-upgrade google-chrome-stable

# Force a Chromium update on Fedora
sudo dnf upgrade --refresh chromium