CVE-2021-39762
📋 TL;DR
CVE-2021-39762 is an integer overflow vulnerability in Android's tremolo audio decoder that could allow remote attackers to read memory beyond intended boundaries. This could lead to information disclosure without requiring user interaction or additional privileges. Only Android 12L devices are affected.
💻 Affected Systems
- Android
📦 What is this software?
Android by Google
⚠️ Risk & Real-World Impact
Worst Case
Remote attacker could read sensitive memory contents from the tremolo audio decoder process, potentially exposing cryptographic keys, authentication tokens, or other protected data.
Likely Case
Information disclosure of limited memory contents from the audio decoder process, potentially revealing system information or application data.
If Mitigated
No impact if patched or if affected component is not exposed to untrusted audio files.
🎯 Exploit Status
No authentication required, but exploitation requires delivering a specially crafted audio file to trigger the integer overflow.
🛠️ 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. Reboot the device after installation.
🔧 Temporary Workarounds
Disable automatic media processing
androidPrevent automatic processing of audio files from untrusted sources
Use alternative audio players
androidUse third-party audio players that don't use the vulnerable tremolo decoder
🧯 If You Can't Patch
- Restrict access to audio files from untrusted sources
- Implement network filtering to block malicious audio file delivery
🔍 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:
adb shell getprop ro.build.version.release && adb shell getprop ro.build.version.security_patchVerify Fix Applied:
Verify Android version is 12L with security patch level March 2022 or later in Settings > About phone > Android version.📡 Detection & Monitoring
Log Indicators:
- Audio decoder crashes
- Memory access violations in media server logs
Network Indicators:
- Unusual audio file downloads
- Suspicious media file transfers
SIEM Query:
source="android_logs" AND (process="mediaserver" OR process="audioserver") AND (event="crash" OR event="segfault")