CVE-2021-0577
📋 TL;DR
CVE-2021-0577 is a heap buffer overflow vulnerability in Android's FLV extractor component that allows local privilege escalation without user interaction. Attackers can exploit this to gain elevated system privileges on vulnerable Android devices. This affects Android devices with specific System-on-Chip (SoC) implementations.
💻 Affected Systems
- Android devices with specific System-on-Chip implementations
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to execute arbitrary code with system privileges, install persistent malware, access all user data, and control device functions.
Likely Case
Local privilege escalation allowing malware to gain higher permissions than originally granted, potentially enabling data theft, surveillance, or further system exploitation.
If Mitigated
Minimal impact if devices are patched or have security controls like SELinux enforcing mode and app sandboxing properly configured.
🎯 Exploit Status
Exploitation requires local access to the device. The vulnerability is in media parsing, so specially crafted FLV files could trigger the overflow when processed by the system.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Android Security Bulletin July 2021 patches
Vendor Advisory: https://source.android.com/security/bulletin/2021-07-01
Restart Required: Yes
Instructions:
1. Check for Android system updates in Settings > System > System update. 2. Install the July 2021 Android security patch. 3. Reboot the device after installation. 4. Verify the patch is applied by checking the Android security patch level in Settings > About phone.
🔧 Temporary Workarounds
Disable FLV file processing
androidPrevent FLV files from being processed by the system media framework
Not applicable - requires system-level configuration changes
Restrict media file sources
androidOnly allow media files from trusted sources and disable automatic media parsing
Not applicable - policy-based control
🧯 If You Can't Patch
- Implement application allowlisting to prevent untrusted apps from processing media files
- Use mobile device management (MDM) solutions to restrict media file handling and monitor for suspicious activity
🔍 How to Verify
Check if Vulnerable:
Check Android security patch level in Settings > About phone. If patch level is before July 2021, the device may be vulnerable.Check Version:
adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify the Android security patch level shows 'July 5, 2021' or later in Settings > About phone > Android security patch level.📡 Detection & Monitoring
Log Indicators:
- Crash logs from media server processes
- SELinux denials related to media parsing
- Unexpected process privilege escalation
Network Indicators:
- Not applicable - local exploitation only
SIEM Query:
Not applicable for network detection - focus on device logs for media server crashes or privilege escalation events