CVE-2021-0936
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Android kernel's USB accessory driver that could allow local privilege escalation. An attacker with local access could exploit memory corruption to gain elevated privileges without user interaction. This affects Android devices with vulnerable kernel versions.
💻 Affected Systems
- Android devices with vulnerable kernel
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise with root privileges, allowing installation of persistent malware, data theft, and bypassing of security controls.
Likely Case
Local privilege escalation from a limited user or app context to kernel-level access, enabling further system exploitation.
If Mitigated
Limited impact if device is fully patched, has SELinux enforcing mode, and proper app sandboxing.
🎯 Exploit Status
Requires local access and knowledge of kernel memory layout. No public exploit code identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: October 2021 Android Security Patch Level or later
Vendor Advisory: https://source.android.com/security/bulletin/pixel/2021-10-01
Restart Required: Yes
Instructions:
1. Check for system updates in Settings > System > Advanced > System update. 2. Install October 2021 or later security patch. 3. Reboot device after installation.
🔧 Temporary Workarounds
Disable USB debugging/accessory mode
androidPrevents exploitation by disabling the vulnerable USB accessory functionality
Settings > System > Developer options > USB debugging (OFF)
Settings > Connected devices > USB > Select 'No data transfer'
🧯 If You Can't Patch
- Restrict physical access to devices and implement strict app installation policies
- Enable SELinux enforcing mode and implement least privilege principles for apps
🔍 How to Verify
Check if Vulnerable:
Check Android security patch level: Settings > About phone > Android security patch level. If before October 2021, device is vulnerable.Check Version:
adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify Android security patch level shows October 2021 or later date.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- USB accessory driver crash logs
- SELinux denials related to f_accessory.c
Network Indicators:
- No network indicators - local exploit only
SIEM Query:
No applicable network SIEM query - monitor device logs for kernel crashes or privilege escalation attempts