CVE-2023-5487: Google Chrome Auth Bypass Vulnerability

CVE-2023-5487 Overview

CVE-2023-5487 is an inappropriate implementation vulnerability in the Fullscreen component of Google Chrome prior to version 118.0.5993.70. This security flaw allows an attacker who convinces a user to install a malicious extension to bypass navigation restrictions via a crafted Chrome Extension.

Critical Impact

A malicious Chrome extension can exploit this vulnerability to bypass browser navigation restrictions, potentially enabling phishing attacks, credential theft, or redirection to malicious websites while the browser is in fullscreen mode.

Affected Products

• Google Chrome prior to version 118.0.5993.70
• Fedora 37 (via bundled Chromium)
• Fedora 38 (via bundled Chromium)

Discovery Timeline

• October 11, 2023 - CVE-2023-5487 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-5487

Vulnerability Analysis

This vulnerability stems from an inappropriate implementation in the Fullscreen API within Google Chrome. The flaw exists in how Chrome handles navigation restrictions when the browser enters fullscreen mode in conjunction with Chrome extension capabilities.

When a user installs a malicious extension, that extension can exploit the improper implementation to circumvent the browser's built-in navigation security controls. This is particularly dangerous because fullscreen mode is designed to provide an immersive experience, and users may not notice subtle UI changes or navigational anomalies that could indicate they've been redirected to a malicious site.

The attack requires user interaction—specifically, the victim must be convinced to install a malicious Chrome extension. Once installed, the extension can leverage the Fullscreen API implementation flaw to bypass restrictions that would normally prevent unauthorized navigation.

Root Cause

The root cause of CVE-2023-5487 is an inappropriate implementation in the Fullscreen component that fails to properly enforce navigation restrictions when interacting with Chrome extension APIs. The Fullscreen implementation did not adequately validate or restrict navigation requests originating from extensions, creating a security gap that could be exploited through crafted extension code.

Attack Vector

The attack vector for this vulnerability is network-based and requires user interaction. An attacker must:

1. Develop a malicious Chrome extension that exploits the Fullscreen implementation flaw
2. Distribute the extension and convince users to install it (via social engineering, fake extension stores, or compromised legitimate extensions)
3. Once installed, the extension can bypass navigation restrictions to redirect users to attacker-controlled pages

The vulnerability allows high integrity impact as attackers can manipulate the user's browsing context without their knowledge or consent while in fullscreen mode.

Detection Methods for CVE-2023-5487

Indicators of Compromise

• Unexpected browser behavior when entering fullscreen mode
• Navigation to unknown or suspicious URLs without explicit user action
• Recently installed Chrome extensions from untrusted sources
• Extensions requesting excessive permissions related to navigation or fullscreen capabilities

Detection Strategies

• Monitor installed Chrome extensions for suspicious permissions, particularly those requesting access to fullscreen APIs or navigation controls
• Implement browser extension whitelisting policies to prevent unauthorized extension installations
• Review browser logs for abnormal navigation patterns, especially those occurring during fullscreen sessions
• Use endpoint detection solutions to identify malicious extension behavior patterns

Monitoring Recommendations

• Enable Chrome browser telemetry and centralize logging for enterprise environments
• Configure alerts for new extension installations across managed endpoints
• Monitor for extensions with unusual permission combinations involving tabs, navigation, and fullscreen capabilities
• Implement regular audits of installed browser extensions across the organization

How to Mitigate CVE-2023-5487

Immediate Actions Required

• Update Google Chrome to version 118.0.5993.70 or later immediately
• Review and audit all installed Chrome extensions, removing any untrusted or unnecessary extensions
• Enable Chrome's Enhanced Safe Browsing feature to protect against malicious extensions
• Implement enterprise browser policies to restrict extension installations to approved sources only

Patch Information

Google has addressed this vulnerability in Chrome version 118.0.5993.70. The fix corrects the inappropriate implementation in the Fullscreen component to properly enforce navigation restrictions regardless of extension API interactions.

For detailed patch information, refer to the Google Chrome Stable Channel Update. Additional security advisories have been released by Debian Security Advisory DSA-5526, Gentoo GLSA 202311-11, and Fedora via their package announcement lists.

Workarounds

• Disable or uninstall all non-essential Chrome extensions until the browser can be updated
• Avoid entering fullscreen mode when using untrusted extensions
• Implement browser extension whitelisting via Chrome Enterprise policies using ExtensionInstallAllowlist and ExtensionInstallBlocklist
• Use Chrome's --disable-extensions flag for high-security sessions where extensions are not required

# Chrome Enterprise policy configuration example
# Add to Chrome policies to restrict extension installations

# For Linux, create/edit: /etc/opt/chrome/policies/managed/extension_policy.json
{
  "ExtensionInstallBlocklist": ["*"],
  "ExtensionInstallAllowlist": ["<approved-extension-id-1>", "<approved-extension-id-2>"],
  "ExtensionInstallSources": ["https://clients2.google.com/service/update2/crx"]
}