CVE-2021-0799: Android Privilege Escalation Vulnerability

CVE-2021-0799 Overview

CVE-2021-0799 is a local privilege escalation vulnerability in Android's ActivityThread.java component. The vulnerability allows an attacker to collide content provider authorities, enabling unauthorized privilege escalation without requiring any additional execution privileges or user interaction.

Critical Impact

This vulnerability enables local privilege escalation on Android 12 devices through content provider authority collision, potentially allowing malicious applications to gain elevated system privileges without user awareness.

Affected Products

• Google Android 12.0

Discovery Timeline

• 2021-12-15 - CVE CVE-2021-0799 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-0799

Vulnerability Analysis

The vulnerability resides in the ActivityThread.java file within Android's application framework layer. Content providers in Android use authorities as unique identifiers to distinguish between different providers. This vulnerability allows a malicious application to collide with legitimate content provider authorities, effectively hijacking or impersonating trusted content providers.

When an authority collision occurs, the Android system may route content provider requests to the malicious provider instead of the legitimate one. This allows the attacker to intercept sensitive data, manipulate responses, or leverage the elevated permissions of the targeted content provider to perform privileged operations.

Root Cause

The root cause stems from insufficient validation of content provider authorities during registration and resolution within the ActivityThread.java component. The Android framework fails to properly enforce uniqueness guarantees for content provider authorities, allowing a malicious application to register a provider with an authority that conflicts with existing system or application providers.

Attack Vector

The attack requires local access to the target Android device, typically through a malicious application installed on the device. The attacker application does not need any special permissions to exploit this vulnerability. The attack flow involves:

1. The malicious application registers a content provider with an authority designed to collide with a legitimate provider
2. When other applications or system components attempt to query the legitimate provider, the system may resolve to the malicious provider instead
3. The attacker intercepts requests and responses, gaining access to sensitive data or elevated privileges
4. No user interaction is required for the exploitation to succeed

The local attack vector combined with low attack complexity makes this vulnerability particularly concerning for enterprise environments where device security is paramount.

Detection Methods for CVE-2021-0799

Indicators of Compromise

• Unusual content provider registrations from non-system applications attempting to use system-level authorities
• Applications with content provider declarations that mirror legitimate system or popular application authorities
• Unexpected inter-process communication patterns between apps and system services
• Anomalous permission escalation behavior from installed applications

Detection Strategies

• Monitor for applications attempting to register content providers with authorities matching system components
• Implement behavioral analysis to detect applications accessing resources beyond their declared permissions
• Review installed application manifests for suspicious content provider authority declarations
• Deploy runtime application self-protection (RASP) solutions to detect privilege escalation attempts

Monitoring Recommendations

• Enable verbose logging for content provider resolution activities on managed devices
• Implement MDM solutions with application vetting capabilities to screen for malicious authority declarations
• Monitor Android system logs for content provider registration conflicts or errors
• Establish baseline behavior for system component communications and alert on deviations

How to Mitigate CVE-2021-0799

Immediate Actions Required

• Update affected Android 12 devices to the latest security patch level that addresses this vulnerability
• Review installed applications for suspicious content provider declarations
• Restrict application installations to verified sources (Google Play Store or enterprise app stores)
• Enable Google Play Protect to scan for potentially harmful applications

Patch Information

Google has addressed this vulnerability in the Android Security Bulletin November 2021. The fix is tracked under Android ID A-197647956. Device manufacturers should incorporate the November 2021 security patches into their firmware updates.

Organizations should verify their devices have received security patches dated November 2021 or later. The patch implements proper authority validation and collision prevention in the ActivityThread.java component.

Workarounds

• Implement application whitelisting policies to prevent installation of untrusted applications
• Use Mobile Device Management (MDM) solutions to enforce security policies and restrict app installations
• Disable installation from unknown sources at the device or enterprise policy level
• Consider containerization solutions for sensitive enterprise applications to isolate them from potentially malicious apps
• Perform regular security audits of installed applications on managed devices

# Check Android security patch level via ADB
adb shell getprop ro.build.version.security_patch

# Verify device is running November 2021 or later patches
# Expected output: 2021-11-01 or later date