CVE-2023-21241
📋 TL;DR
This vulnerability allows local privilege escalation on Android devices via an integer overflow in the NFC stack's rw_i93.cc component. Attackers can exploit this without user interaction or additional permissions, potentially gaining elevated system access. Affects Android devices with vulnerable NFC implementations.
💻 Affected Systems
- Android devices with NFC capabilities
📦 What is this software?
Android by Google
Android by Google
Android by Google
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise with root/system-level access, allowing installation of persistent malware, data theft, and bypassing security controls.
Likely Case
Local privilege escalation to gain elevated permissions for further attacks, potentially leading to data access or persistence mechanisms.
If Mitigated
Limited impact with proper patching and security controls; exploitation attempts would be detected and blocked.
🎯 Exploit Status
No user interaction required, but requires local access or malicious app execution. Technical details are public in the Android source code.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: July 2023 Android Security Patch Level or later
Vendor Advisory: https://source.android.com/security/bulletin/2023-07-01
Restart Required: Yes
Instructions:
1. Check for system updates in Settings > System > System update. 2. Apply the July 2023 or later security patch. 3. Restart the device after installation.
🔧 Temporary Workarounds
Disable NFC
androidTemporarily disable NFC functionality to prevent exploitation
adb shell settings put secure nfc_on 0
Settings > Connected devices > Connection preferences > NFC (toggle off)
🧯 If You Can't Patch
- Disable NFC functionality on all affected devices
- Implement application allowlisting to prevent malicious apps from exploiting the vulnerability
🔍 How to Verify
Check if Vulnerable:
Check Android security patch level: Settings > About phone > Android version > Security patch level. If before July 2023, device is vulnerable.Check Version:
adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify security patch level shows July 2023 or later. Check NFC functionality still works properly after patch.📡 Detection & Monitoring
Log Indicators:
- Unusual NFC stack crashes in system logs
- Privilege escalation attempts via NFC services
Network Indicators:
- Unexpected NFC communication patterns
- Malformed NFC tag emulation attempts
SIEM Query:
source="android_system" AND (process="com.android.nfc" OR component="NfcService") AND (event="crash" OR event="privilege")🔗 References
- https://android.googlesource.com/platform/system/nfc/+/907d17eeefec6f672ea824e126406e6d8f6b56d8
- https://source.android.com/security/bulletin/2023-07-01
- https://android.googlesource.com/platform/system/nfc/+/907d17eeefec6f672ea824e126406e6d8f6b56d8
- https://source.android.com/security/bulletin/2023-07-01
