CVE-2023-20983: Google Android Information Disclosure Flaw

CVE-2023-20983 Overview

CVE-2023-20983 is an out-of-bounds read vulnerability discovered in the Android Bluetooth stack, specifically within the btm_ble_rand_enc_complete function located in btm_ble.cc. The vulnerability stems from a missing bounds check that could allow an attacker with System execution privileges to access memory beyond the intended buffer boundaries, potentially leading to local information disclosure.

Critical Impact

Local information disclosure affecting Android 13 devices through improper memory access in the Bluetooth Low Energy (BLE) subsystem. Exploitation does not require user interaction.

Affected Products

• Google Android 13.0

Discovery Timeline

• 2023-03-24 - CVE-2023-20983 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-20983

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a common memory safety issue that occurs when software reads data past the boundaries of an allocated buffer. In the context of btm_ble_rand_enc_complete, the function processes random encryption completion events in the Bluetooth Low Energy stack without properly validating the bounds of the data being accessed.

The vulnerability exists in the Android Bluetooth Manager (BTM) module, which handles BLE encryption operations. When processing encryption completion callbacks, the function fails to verify that the data length falls within expected boundaries before reading from the buffer. This oversight allows reading beyond allocated memory regions.

Root Cause

The root cause is a missing bounds check in the btm_ble_rand_enc_complete function within btm_ble.cc. The function processes encryption-related data from the BLE controller without verifying that the received data length is within acceptable limits. This allows out-of-bounds memory access when malformed or unexpected data is processed.

Attack Vector

The attack requires local access to the device with System execution privileges. An attacker with elevated privileges could potentially trigger the vulnerable code path through the Bluetooth subsystem to read sensitive information from adjacent memory regions. The attack does not require any user interaction, making it exploitable in automated scenarios once the prerequisite privileges are obtained.

The vulnerability manifests when the BLE random encryption completion handler processes data without proper length validation. Attackers with System-level access could craft specific Bluetooth operations that trigger the vulnerable code path, causing the function to read beyond the intended buffer boundaries and potentially exposing sensitive kernel or system memory contents.

Detection Methods for CVE-2023-20983

Indicators of Compromise

• Unusual Bluetooth service crashes or restarts indicating potential exploitation attempts
• Abnormal memory access patterns in the btm_ble.cc module during BLE operations
• System logs showing unexpected behavior in the Bluetooth Low Energy encryption subsystem
• Evidence of privilege escalation attempts targeting Bluetooth system services

Detection Strategies

• Monitor Android system logs for Bluetooth stack exceptions or memory access violations
• Implement runtime memory protection mechanisms to detect out-of-bounds read attempts
• Deploy endpoint detection solutions capable of monitoring Bluetooth subsystem behavior
• Analyze system audit logs for suspicious process activity involving Bluetooth services with System privileges

Monitoring Recommendations

• Enable verbose logging for the Android Bluetooth service to capture potential exploitation attempts
• Monitor for unusual process behavior involving the Bluetooth system service
• Implement SentinelOne Singularity Platform for comprehensive endpoint visibility and threat detection
• Review device security patches to ensure the June 2023 Android security bulletin has been applied

How to Mitigate CVE-2023-20983

Immediate Actions Required

• Apply the Android security patch from the June 2023 security bulletin immediately
• Verify all Android 13 devices in your environment are updated to the patched version
• Review device management policies to ensure automatic security updates are enabled
• Audit system privilege assignments to minimize exposure to the required attack prerequisites

Patch Information

Google has addressed this vulnerability in the Android Security Bulletin for June 2023. The fix adds proper bounds checking to the btm_ble_rand_enc_complete function to prevent out-of-bounds read operations. Organizations should ensure all Android 13 devices receive this security update through their device management solutions.

The vulnerability is tracked internally by Google as Android ID A-260569449.

Workarounds

• Limit applications and services with System execution privileges to reduce attack surface
• Implement mobile device management (MDM) solutions to enforce security configurations
• Consider disabling Bluetooth on devices where it is not required until patches can be applied
• Isolate unpatched devices from sensitive networks and data

# Verify Android security patch level
adb shell getprop ro.build.version.security_patch
# Expected output should be 2023-06-01 or later for patched devices