CVE-2021-39771
📋 TL;DR
This vulnerability in Android Settings allows an attacker to misrepresent which app is requesting to add a Wi-Fi network due to improper input validation. This could lead to local privilege escalation without requiring additional execution privileges, though user interaction is needed for exploitation. Only Android 12L devices are affected.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
An attacker could trick a user into granting Wi-Fi network addition permissions to a malicious app, potentially allowing network interception, credential theft, or further device compromise.
Likely Case
A malicious app could add unauthorized Wi-Fi networks to the device, potentially leading to man-in-the-middle attacks or network-based exploitation.
If Mitigated
With proper user awareness and app vetting, users would deny suspicious Wi-Fi addition requests, preventing exploitation.
🎯 Exploit Status
Requires user interaction and a malicious app to be installed. No public exploit code known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Bulletin for Android 12L (March 2022 or later)
Vendor Advisory: https://source.android.com/security/bulletin/android-12l
Restart Required: Yes
Instructions:
1. Check for Android system updates in Settings > System > System update. 2. Install the latest security update. 3. Restart the device after installation.
🔧 Temporary Workarounds
Disable unknown app installations
androidPrevent installation of apps from unknown sources to reduce risk of malicious apps.
Settings > Security > Install unknown apps > Disable for all apps
Review Wi-Fi network requests carefully
androidAlways verify which app is requesting to add Wi-Fi networks and deny suspicious requests.
🧯 If You Can't Patch
- Only install apps from trusted sources like Google Play Store
- Educate users to carefully review Wi-Fi network addition requests and deny any suspicious ones
🔍 How to Verify
Check if Vulnerable:
Check Android version in Settings > About phone > Android version. If it shows Android 12L and security patch level is before March 2022, device is vulnerable.Check Version:
Settings > About phone > Android versionVerify Fix Applied:
Verify Android version is 12L and security patch level is March 2022 or later in Settings > About phone > Android version.📡 Detection & Monitoring
Log Indicators:
- Unusual Wi-Fi network addition requests in system logs
- Multiple failed Wi-Fi addition attempts from unknown apps
Network Indicators:
- Unexpected Wi-Fi networks appearing on device
- Network traffic to suspicious access points
SIEM Query:
Not typically applicable for mobile device logs in enterprise SIEMs