CVE-2021-30626: Google Chrome Buffer Overflow Vulnerability

CVE-2021-30626 Overview

CVE-2021-30626 is an out-of-bounds memory access vulnerability in the ANGLE (Almost Native Graphics Layer Engine) component of Google Chrome prior to version 93.0.4577.82. This vulnerability allows a remote attacker to potentially exploit heap corruption via a crafted HTML page, which could lead to arbitrary code execution within the context of the browser.

Critical Impact

Remote attackers can achieve heap corruption through specially crafted web content, potentially leading to arbitrary code execution with user privileges.

Affected Products

• Google Chrome versions prior to 93.0.4577.82
• Fedora 33 (via bundled Chromium package)
• Fedora 35 (via bundled Chromium package)

Discovery Timeline

• October 8, 2021 - CVE-2021-30626 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2021-30626

Vulnerability Analysis

This vulnerability resides in the ANGLE component of Google Chrome, which serves as an abstraction layer for OpenGL ES rendering, translating OpenGL calls to the underlying graphics API (DirectX on Windows, OpenGL on other platforms). The out-of-bounds memory access occurs when processing specific graphics operations, leading to heap corruption.

The flaw is classified under CWE-787 (Out-of-bounds Write), indicating that the vulnerable code writes data past the end or before the beginning of the intended buffer. When triggered through a crafted HTML page, an attacker can manipulate memory regions beyond allocated boundaries, potentially overwriting critical data structures or function pointers.

Root Cause

The root cause stems from improper bounds checking within the ANGLE graphics layer. When processing certain WebGL or graphics-related operations, the component fails to properly validate array indices or buffer sizes before performing write operations. This allows malicious web content to trigger writes to unintended memory locations, corrupting the heap and potentially enabling code execution.

Attack Vector

The attack vector is network-based and requires user interaction—specifically, a victim must navigate to a malicious webpage containing the crafted HTML/JavaScript payload. The attacker does not need any privileges on the target system. Once the victim loads the malicious page, the crafted content triggers the out-of-bounds memory access in the ANGLE rendering pipeline.

The exploitation flow typically involves:

1. Attacker hosts malicious webpage with crafted WebGL/graphics content
2. Victim navigates to the malicious page
3. ANGLE processes the malicious graphics commands
4. Out-of-bounds write corrupts heap memory
5. Attacker achieves code execution within the Chrome sandbox

The vulnerability mechanism exploits improper bounds validation in ANGLE's graphics processing pipeline. When specific WebGL operations are performed, the component may write beyond allocated buffer boundaries, leading to heap corruption. Attackers can craft malicious HTML pages that trigger these conditions through carefully constructed graphics operations. For detailed technical information, see the Chromium Bug Report #1241036.

Detection Methods for CVE-2021-30626

Indicators of Compromise

• Unexpected Chrome renderer process crashes, particularly during WebGL-heavy page loads
• Memory access violation errors in system logs associated with Chrome's GPU process
• Suspicious network connections to unknown domains followed by browser instability
• Anomalous heap memory patterns in Chrome processes

Detection Strategies

• Monitor for Chrome versions prior to 93.0.4577.82 across the enterprise using asset management tools
• Implement browser extension policies that can detect and block known malicious WebGL patterns
• Deploy endpoint detection and response (EDR) solutions capable of identifying heap spray and corruption techniques
• Analyze web proxy logs for access to domains associated with exploit kit activity

Monitoring Recommendations

• Enable Chrome's built-in crash reporting and monitor for ANGLE-related crashes
• Configure SIEM rules to correlate browser crashes with preceding network activity
• Monitor for child process spawning from Chrome renderer processes, which may indicate successful exploitation
• Track Chrome version deployment across endpoints to identify vulnerable installations

How to Mitigate CVE-2021-30626

Immediate Actions Required

• Update Google Chrome to version 93.0.4577.82 or later immediately
• Enable automatic updates for Chrome to ensure timely patch deployment
• Review and apply Fedora security updates for affected Fedora 33 and Fedora 35 systems
• Consider temporarily disabling WebGL in Chrome for high-risk environments until patching is complete

Patch Information

Google addressed this vulnerability in the Chrome 93 stable channel release. The fix was announced in the Google Chrome Desktop Update blog post. Technical details of the fix are tracked in Chromium Bug Report #1241036.

For Fedora users, security updates are available through the standard package management system. See the Fedora Package Announcement for more details.

Workarounds

• Disable WebGL by navigating to chrome://flags/#disable-webgl and enabling the flag to disable WebGL
• Use browser isolation technologies to contain potential exploitation attempts
• Implement network-level filtering to block access to known malicious domains
• Consider deploying application whitelisting to prevent unauthorized code execution

# Configuration example - Disable WebGL via Chrome Enterprise Policy
# For Linux systems, create/edit the managed policies file:
sudo mkdir -p /etc/opt/chrome/policies/managed
echo '{"WebGLAllowed": false}' | sudo tee /etc/opt/chrome/policies/managed/webgl_policy.json

# For Windows, set via Group Policy or registry:
# HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome
# WebGLAllowed = 0 (DWORD)