CVE-2021-1021
📋 TL;DR
This Android vulnerability allows a malicious app with user execution privileges to disable notifications for any user on the device through improper input validation in the notification system. It affects Android 12 devices and requires user interaction for exploitation, potentially leading to local privilege escalation.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
An attacker could disable critical security notifications, hide malicious activity, and potentially chain with other vulnerabilities to gain higher privileges on the device.
Likely Case
Malicious apps could suppress security warnings and notifications to conceal their activities from users while operating with standard app permissions.
If Mitigated
With proper app vetting and security controls, exploitation would be limited to isolated app sandboxes without system-wide impact.
🎯 Exploit Status
Requires user to install and interact with a malicious app. The vulnerability is in the notification service's input validation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Patch Level 2021-12-01 or later
Vendor Advisory: https://source.android.com/security/bulletin/pixel/2021-12-01
Restart Required: Yes
Instructions:
1. Check for system updates in Settings > System > System update. 2. Install the December 2021 Android security patch or later. 3. Restart the device after installation.
🔧 Temporary Workarounds
Disable unknown app sources
androidPrevent installation of apps from untrusted sources to reduce risk of malicious app installation.
Settings > Security > Install unknown apps > Disable for all apps
Use Google Play Protect
androidEnable Google's built-in malware scanning for apps.
Settings > Security > Google Play Protect > Scan device for security threats
🧯 If You Can't Patch
- Restrict app installations to Google Play Store only
- Monitor for suspicious apps that request excessive notification permissions
🔍 How to Verify
Check if Vulnerable:
Check Android version in Settings > About phone > Android version. If it shows Android 12 with security patch level before December 2021, the device is vulnerable.Check Version:
adb shell getprop ro.build.version.release && adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify the security patch level is December 2021 or later in Settings > About phone > Android security patch level.📡 Detection & Monitoring
Log Indicators:
- Unusual notification service crashes
- Apps attempting to modify notification settings for other users
Network Indicators:
- No direct network indicators as this is a local privilege escalation
SIEM Query:
No standard SIEM query available for mobile device logs