CVE-2020-0022: Google Android Bluetooth RCE Vulnerability

CVE-2020-0022 Overview

CVE-2020-0022 is a critical out-of-bounds write vulnerability in the Android Bluetooth stack, specifically within the reassemble_and_dispatch function of packet_fragmenter.cc. This vulnerability arises from an incorrect bounds calculation during Bluetooth packet fragment reassembly, allowing a remote attacker within Bluetooth range to execute arbitrary code on the target device without any user interaction or additional privileges.

The vulnerability is particularly dangerous because it can be exploited wirelessly over Bluetooth, requiring only that the target device has Bluetooth enabled and is within proximity of the attacker. Successful exploitation could result in complete device compromise, including data theft, malware installation, or device takeover.

Critical Impact

Remote code execution over Bluetooth with no user interaction required. An attacker within Bluetooth range can compromise vulnerable Android devices running versions 8.0 through 10.0, as well as numerous Huawei smartphones with affected firmware.

Affected Products

• Google Android 8.0, 8.1, 9.0, and 10.0
• Huawei Mate 20, Mate 20 Pro, Mate 20 X series
• Huawei P20, P20 Pro, P30, P30 Pro series
• Huawei Mate 30, Mate 30 Pro, Mate 30 5G series
• Huawei Nova 3, Nova Lite 3
• Huawei Honor 8A, Honor 8X, Honor View 20
• Huawei P Smart, P Smart 2019
• Huawei Y6 2019, Y6 Pro 2019, Y9 2019

Discovery Timeline

• February 13, 2020 - CVE-2020-0022 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-0022

Vulnerability Analysis

This vulnerability exists in the Bluetooth packet fragmentation and reassembly logic within Android's Bluetooth stack. The reassemble_and_dispatch function in packet_fragmenter.cc is responsible for handling fragmented Bluetooth packets and reconstructing them into complete data units. Due to incorrect bounds calculation during this reassembly process, an attacker can craft malicious Bluetooth packets that trigger an out-of-bounds write condition.

The flaw is classified under CWE-682 (Incorrect Calculation), as the vulnerability stems from an improper mathematical computation when determining buffer boundaries during packet reassembly. This allows data to be written beyond the allocated memory region, potentially corrupting adjacent memory structures or overwriting critical execution data.

Root Cause

The root cause of CVE-2020-0022 lies in the bounds calculation logic within the packet fragmenter component. When reassembling fragmented Bluetooth L2CAP (Logical Link Control and Adaptation Protocol) packets, the code fails to properly validate the total length of incoming fragments against the allocated buffer size. This calculation error allows specially crafted packet fragments to exceed the expected boundary, resulting in memory corruption through an out-of-bounds write operation.

Attack Vector

The attack is conducted over an adjacent network (Bluetooth), meaning an attacker must be within Bluetooth radio range of the target device (typically 10-100 meters depending on the Bluetooth class). The attack requires:

1. Target device has Bluetooth enabled and is discoverable or the attacker knows the device's Bluetooth MAC address
2. Attacker sends specially crafted L2CAP packet fragments to the target
3. The malformed fragments exploit the bounds calculation error during reassembly
4. Out-of-bounds write occurs, potentially achieving arbitrary code execution

The vulnerability requires no authentication, no user interaction, and no special privileges on the target device. The attacker can silently compromise the device while the victim is unaware of the attack.

Detection Methods for CVE-2020-0022

Indicators of Compromise

• Unusual Bluetooth connection attempts from unknown or suspicious MAC addresses
• Bluetooth service crashes or unexpected restarts of the Bluetooth daemon
• Abnormal memory allocation patterns in the Bluetooth stack processes
• Unexplained device behavior following periods of Bluetooth connectivity

Detection Strategies

• Monitor system logs for Bluetooth-related crashes, particularly in com.android.bluetooth process
• Deploy network-level Bluetooth monitoring to detect anomalous packet patterns or oversized L2CAP fragments
• Implement endpoint detection rules that alert on unexpected Bluetooth service behavior
• Review device firmware versions against known vulnerable versions listed in security bulletins

Monitoring Recommendations

• Enable enhanced Bluetooth logging on managed enterprise devices where possible
• Monitor for signs of post-exploitation activity such as new applications, changed permissions, or data exfiltration
• Implement mobile device management (MDM) solutions to track device patch levels and Bluetooth configuration status
• Conduct regular security assessments of mobile device fleets to identify unpatched devices

How to Mitigate CVE-2020-0022

Immediate Actions Required

• Apply the February 2020 Android Security Patch immediately on all affected devices
• Disable Bluetooth on vulnerable devices until patches can be applied
• For Huawei devices, apply firmware updates as specified in the Huawei Security Advisory
• Prioritize patching devices that frequently operate in public or untrusted environments

Patch Information

Google addressed this vulnerability in the Android Security Bulletin - February 2020. The patch corrects the bounds calculation in the reassemble_and_dispatch function to prevent out-of-bounds write conditions during Bluetooth packet fragment reassembly.

For Android devices, ensure the security patch level is dated February 2020 or later. Huawei has released corresponding firmware updates for affected smartphone models. Enterprise administrators should use MDM solutions to verify patch compliance across their device fleets.

Workarounds

• Disable Bluetooth completely when not actively in use to eliminate the attack surface
• Keep devices in non-discoverable mode to reduce exposure to opportunistic attackers
• Avoid using Bluetooth in high-risk environments such as public spaces or conferences until patches are applied
• Consider implementing Bluetooth usage policies that restrict connectivity to known, trusted devices only

# Check Android security patch level via ADB
adb shell getprop ro.build.version.security_patch

# Disable Bluetooth via ADB (requires root or debugging access)
adb shell settings put global bluetooth_on 0
adb shell am force-stop com.android.bluetooth