CVE-2021-0538 – This vulnerability allows attackers to trick us... (How to Fix)

Q: What is the severity of CVE-2021-0538?

CVE-2021-0538 has a CVSS score of 7.3 (HIGH). This vulnerability allows attackers to trick users into tapping on malicious overlays that exit emergency callback mode, potentially enabling local privilege escalation. It affects Android 11 devices, requiring user interaction and execution privileges for exploitation.

📋 TL;DR

This vulnerability allows attackers to trick users into tapping on malicious overlays that exit emergency callback mode, potentially enabling local privilege escalation. It affects Android 11 devices, requiring user interaction and execution privileges for exploitation.

💻 Affected Systems

Products:

Android

Versions: Android 11

Operating Systems: Android

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects devices running Android 11. Requires user interaction and malicious app installation.

📦 What is this software?

Android by Google

View all CVEs affecting Android →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Attacker gains elevated privileges on the device, potentially accessing sensitive data or installing malware.

🟠

Likely Case

Malicious app tricks user into exiting emergency mode, allowing unauthorized actions or data access.

🟢

If Mitigated

With proper app permissions and user awareness, exploitation becomes difficult.

🌐 Internet-Facing: LOW - Requires local access and user interaction.

🏢 Internal Only: MEDIUM - Malicious apps on corporate devices could exploit this.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires user interaction (tapjacking) and a malicious app with user execution privileges.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Android Security Patch Level 2021-06-01 or later

Vendor Advisory: https://source.android.com/security/bulletin/pixel/2021-06-01

Restart Required: Yes

Instructions:

1. Check for Android system updates in Settings > System > Advanced > System update. 2. Install the June 2021 security patch or later. 3. Restart device after installation.

🔧 Temporary Workarounds

Disable overlay permissions for untrusted apps

android

Prevent apps from drawing over other apps to mitigate tapjacking attacks.

Settings > Apps & notifications > Special app access > Display over other apps > Disable for untrusted apps

🧯 If You Can't Patch

Restrict installation of apps from unknown sources
Use mobile device management (MDM) to control app permissions

🔍 How to Verify

Check if Vulnerable:

Check Android version in Settings > About phone > Android version. If it shows Android 11 and security patch level is before June 2021, device is vulnerable.

Check Version:

Settings > About phone > Android version & Security patch level

Verify Fix Applied:

Verify Android version is 11 and security patch level is 2021-06-01 or later in Settings > About phone.

📡 Detection & Monitoring

Log Indicators:

Unexpected emergency mode exits
App overlay permission abuse logs

Network Indicators:

None - local attack only

SIEM Query:

Look for Android security events related to overlay attacks or emergency mode exits

📊 Metadata

CVE ID: CVE-2021-0538

CVSS v3 Score: 7.3 (HIGH)

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

CWE: CWE-1021

Published: June 22, 2021

Last Updated: November 21, 2024

🔗 References

https://source.android.com/security/bulletin/pixel/2021-06-01 Vendor Advisory
https://source.android.com/security/bulletin/pixel/2021-06-01 Vendor Advisory

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🔗 Related Vulnerabilities

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