CVE-2023-35681: Google Android RCE Vulnerability

CVE-2023-35681 Overview

CVE-2023-35681 is a critical integer overflow vulnerability in Google Android's Bluetooth stack, specifically in the eatt_l2cap_reconfig_completed function within eatt_impl.h. This vulnerability results in an out-of-bounds write condition that can be exploited to achieve remote code execution. The vulnerability requires no user interaction and no additional execution privileges, making it particularly dangerous for Android devices with Bluetooth enabled.

Critical Impact

Remote code execution via Bluetooth without user interaction, potentially allowing complete device compromise on affected Android devices.

Affected Products

• Google Android 13.0

Discovery Timeline

• 2023-09-11 - CVE-2023-35681 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-35681

Vulnerability Analysis

This vulnerability exists within the Enhanced Attribute Protocol (EATT) implementation in Android's Bluetooth module. The eatt_l2cap_reconfig_completed function handles L2CAP (Logical Link Control and Adaptation Protocol) reconfiguration events, which are part of the Bluetooth Low Energy (BLE) communication stack.

The flaw is classified as CWE-190 (Integer Overflow or Wraparound). When processing L2CAP reconfiguration data, an arithmetic operation produces an integer overflow condition. This causes the resulting value to wrap around, leading to an undersized buffer allocation or incorrect bounds checking. Subsequent write operations then exceed the allocated buffer boundaries, corrupting adjacent memory structures.

The vulnerability is exploitable over the network via Bluetooth, requires low attack complexity, and needs no privileges or user interaction. An attacker within Bluetooth range could send specially crafted L2CAP packets to trigger the overflow and potentially execute arbitrary code on the target device.

Root Cause

The root cause is an integer overflow in the eatt_l2cap_reconfig_completed function when handling L2CAP reconfiguration completion events. The vulnerable code fails to properly validate integer arithmetic operations before using the result for memory allocation or array indexing. When a malicious value causes the integer to overflow, it wraps to a smaller value, leading to insufficient memory allocation and subsequent out-of-bounds memory writes.

Attack Vector

An attacker can exploit this vulnerability by sending maliciously crafted Bluetooth L2CAP packets to a vulnerable Android device. The attack does not require the victim to take any action—simply having Bluetooth enabled and being within range of the attacker is sufficient. The attacker would craft packets that trigger the integer overflow condition in the EATT L2CAP reconfiguration handler, causing memory corruption that can be leveraged to execute arbitrary code with the privileges of the Bluetooth daemon process.

The vulnerability is accessible via the network attack vector through Bluetooth communication. Due to the lack of required privileges and user interaction, this represents a severe remote code execution threat for any Android 13.0 device with an active Bluetooth interface.

Detection Methods for CVE-2023-35681

Indicators of Compromise

• Unexpected Bluetooth service crashes or restarts on Android devices
• Anomalous L2CAP reconfiguration traffic patterns from unknown or suspicious devices
• Memory corruption indicators in system logs related to the Bluetooth stack
• Unusual process behavior or privilege escalation following Bluetooth activity

Detection Strategies

• Monitor Bluetooth system logs for crash reports in com.android.bluetooth or related components
• Implement network-level monitoring for anomalous Bluetooth L2CAP traffic patterns
• Deploy endpoint detection and response (EDR) solutions capable of detecting memory corruption exploitation attempts
• Review Android security patch levels across managed device fleets to identify unpatched systems

Monitoring Recommendations

• Enable verbose Bluetooth logging on high-value Android devices for forensic analysis
• Implement mobile device management (MDM) solutions to track security patch compliance
• Configure alerting for Bluetooth service anomalies and unexpected process terminations
• Regularly audit connected Bluetooth device lists for unauthorized pairings

How to Mitigate CVE-2023-35681

Immediate Actions Required

• Apply the Android security patch from the September 2023 security bulletin immediately
• Disable Bluetooth on affected devices until patching is complete
• Restrict Bluetooth visibility and pairing to trusted devices only
• Monitor enterprise Android device fleets for patch compliance

Patch Information

Google has addressed this vulnerability in the September 2023 Android Security Bulletin. The fix is available in the Bluetooth module commit d8d95291f16a8f18f8ffbd6322c14686897c5730. Organizations should ensure all Android 13.0 devices are updated to include security patches from September 2023 or later. Refer to the Android Security Bulletin September 2023 for complete details, and the Android Bluetooth Module Commit for the specific code changes.

Workarounds

• Disable Bluetooth functionality entirely on affected devices until patches can be applied
• Implement Bluetooth management policies through MDM to restrict Bluetooth usage in sensitive environments
• Configure devices to non-discoverable mode to reduce attack surface
• Use network segmentation to isolate high-risk mobile devices from critical infrastructure

# Android ADB commands to verify patch level and manage Bluetooth
# Check current security patch level
adb shell getprop ro.build.version.security_patch

# Disable Bluetooth via settings (requires appropriate permissions)
adb shell settings put global bluetooth_on 0

# Verify Bluetooth is disabled
adb shell settings get global bluetooth_on