CVE-2021-0576 – CVE-2021-0576 is an out-of-bounds write vulnera... (How to Fix)

Q: What is the severity of CVE-2021-0576?

CVE-2021-0576 has a CVSS score of 7.8 (HIGH). CVE-2021-0576 is an out-of-bounds write 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.

📋 TL;DR

CVE-2021-0576 is an out-of-bounds write 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

Products:

Android devices with specific System-on-Chip implementations

Versions: Android SoC implementations prior to August 2021 security patches

Operating Systems: Android

Default Config Vulnerable: ⚠️ Yes

Notes: Vulnerability is in the FLV media extractor component; exploitation requires processing of malicious FLV files. Specific SoC implementations vary by device manufacturer.

📦 What is this software?

Android by Google

View all CVEs affecting Android →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete device compromise allowing attackers to execute arbitrary code with system privileges, install persistent malware, access sensitive data, and bypass security controls.

🟠

Likely Case

Local privilege escalation allowing malware to gain higher privileges than initially obtained, potentially enabling data theft, surveillance, or further system exploitation.

🟢

If Mitigated

Limited impact if devices are patched, have SELinux enforcing mode, and follow principle of least privilege for apps.

🌐 Internet-Facing: LOW - This is a local privilege escalation vulnerability requiring local access to the device, not directly exploitable over the internet.

🏢 Internal Only: HIGH - Malicious apps or compromised user sessions can exploit this vulnerability to escalate privileges without user interaction.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and ability to trigger FLV file processing. No public exploit code is available, but the vulnerability is well-documented in Android security bulletins.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Android Security Patch Level August 2021 or later

Vendor Advisory: https://source.android.com/security/bulletin/2021-08-01

Restart Required: Yes

Instructions:

1. Check for system updates in Settings > System > System update. 2. Install August 2021 or later Android security patch. 3. Restart device after installation. 4. Verify patch level in Settings > About phone > Android security patch level.

🔧 Temporary Workarounds

Disable FLV file processing

android

Prevent apps from processing FLV files through content security policies or app restrictions

Enable SELinux enforcing mode

android

Ensure SELinux is in enforcing mode to limit potential damage from privilege escalation

getenforce

🧯 If You Can't Patch

Restrict app installations to trusted sources only (Google Play Store with Play Protect enabled)
Implement mobile device management (MDM) with application whitelisting and security policies

🔍 How to Verify

Check if Vulnerable:

Check Android security patch level in Settings > About phone > Android security patch level. If date is before August 2021, device is likely vulnerable.

Check Version:

adb shell getprop ro.build.version.security_patch

Verify Fix Applied:

Verify Android security patch level shows August 2021 or later date. Check that SELinux is in enforcing mode using 'getenforce' command (requires ADB or terminal access).

📡 Detection & Monitoring

Log Indicators:

SELinux denials related to media server or FLV processing
Abnormal process privilege escalation in system logs
Crash reports from media.extractor or similar processes

Network Indicators:

Unusual FLV file downloads to devices
Suspicious app behavior attempting to access media processing APIs

SIEM Query:

source="android_logs" AND (process="media.extractor" OR process="mediaserver") AND (event="crash" OR event="privilege_escalation")

📊 Metadata

CVE ID: CVE-2021-0576

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-787

Published: August 17, 2021

Last Updated: November 21, 2024

🔗 References

https://source.android.com/security/bulletin/2021-08-01 Vendor Advisory
https://source.android.com/security/bulletin/2021-08-01 Vendor Advisory

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🔗 Related Vulnerabilities

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