CVE-2023-21273: Google Android RCE Vulnerability

CVE-2023-21273 Overview

CVE-2023-21273 is an out-of-bounds write vulnerability in the Android Bluetooth stack, specifically in the SDP_AddAttribute function within sdp_db.cc. The vulnerability exists due to an incorrect bounds check when processing Service Discovery Protocol (SDP) attributes, allowing an attacker within adjacent network proximity to achieve remote code execution without requiring user interaction or additional execution privileges.

Critical Impact

This vulnerability enables remote code execution via Bluetooth from an adjacent network position, requiring no user interaction and no additional privileges, potentially allowing complete compromise of affected Android devices.

Affected Products

• Google Android 11.0
• Google Android 12.0
• Google Android 12.1
• Google Android 13.0

Discovery Timeline

• August 14, 2023 - CVE-2023-21273 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-21273

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), affecting the Bluetooth Service Discovery Protocol (SDP) implementation in Android's Bluetooth module. The flaw resides in the SDP_AddAttribute function located in sdp_db.cc, which is responsible for adding attributes to SDP service records.

The vulnerability can be exploited by an attacker who is within Bluetooth range (adjacent network) of the target device. The attack requires no user interaction, making it particularly dangerous as victims may be completely unaware that their device is being targeted. The adjacent network attack vector indicates that physical proximity is required, typically within standard Bluetooth range of approximately 10 meters for Class 2 devices.

Root Cause

The root cause of CVE-2023-21273 is an incorrect bounds check in the SDP_AddAttribute function. When processing incoming SDP attribute data, the function fails to properly validate the size or boundaries of the data being written to memory. This insufficient validation allows an attacker to craft malicious SDP packets that cause the function to write data beyond the allocated buffer boundaries, resulting in memory corruption.

Attack Vector

The attack is conducted over an adjacent network, specifically via Bluetooth communication. An attacker within Bluetooth range can send specially crafted SDP packets to a vulnerable Android device. The malicious packets exploit the improper bounds checking in SDP_AddAttribute, triggering an out-of-bounds write condition.

The exploitation does not require any privileges on the target system, and the victim does not need to interact with or acknowledge any prompts. This makes the vulnerability suitable for drive-by attacks where an attacker simply needs to be in physical proximity to potential victims. The successful exploitation results in arbitrary code execution in the context of the Bluetooth service process, potentially allowing the attacker to gain persistent access, exfiltrate data, or further compromise the device.

The vulnerability mechanism involves malformed SDP attribute data that bypasses the bounds checking logic. When the Bluetooth stack processes these malicious attributes, it writes attacker-controlled data past the intended buffer boundaries, corrupting adjacent memory and enabling code execution. For complete technical details, refer to the Android Bluetooth Module Update.

Detection Methods for CVE-2023-21273

Indicators of Compromise

• Unusual Bluetooth service crashes or unexpected restarts on Android devices
• Anomalous Bluetooth SDP traffic patterns or malformed SDP attribute requests
• Unexpected processes spawning from Bluetooth-related system services
• Memory corruption indicators in Bluetooth service logs or crash dumps

Detection Strategies

• Monitor Android system logs for Bluetooth service anomalies, particularly crashes in com.android.bluetooth process
• Implement network monitoring for unusual SDP packet patterns at the Bluetooth protocol level
• Deploy endpoint detection solutions capable of identifying memory corruption exploitation attempts
• Utilize Android Enterprise or MDM solutions to track device patch levels and identify vulnerable systems

Monitoring Recommendations

• Enable verbose Bluetooth logging on test devices to identify potential exploitation attempts during security assessments
• Implement centralized logging for Android device crash reports to detect patterns indicating exploitation
• Monitor for unauthorized Bluetooth pairing attempts or connections from unknown devices
• Track Bluetooth module version information across managed device fleets to ensure patch compliance

How to Mitigate CVE-2023-21273

Immediate Actions Required

• Apply the August 2023 Android security patch immediately to all affected Android devices
• Disable Bluetooth on devices that cannot be immediately patched when not actively in use
• Implement Bluetooth visibility restrictions to reduce attack surface
• Remove previously paired Bluetooth devices that are no longer needed

Patch Information

Google has released a security patch addressing this vulnerability in the Android Security Bulletin August 2023. The fix involves correcting the bounds checking logic in the SDP_AddAttribute function to properly validate attribute data before writing to memory.

The specific code changes can be reviewed in the Android Bluetooth Module Update (commit 1e27ef69755a0735278a1c6af130c71a92b94e3f). Device manufacturers should incorporate this patch into their firmware updates, and end users should apply system updates as soon as they become available for their specific device models.

Workarounds

• Disable Bluetooth entirely on devices that cannot be patched until updates are available
• Enable Bluetooth only when actively needed and disable immediately after use
• Avoid using Bluetooth in public or crowded locations where attackers may be present
• Use Android Enterprise policies to enforce Bluetooth restrictions on corporate-managed devices

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

# Disable Bluetooth via ADB (requires root or device owner)
adb shell settings put global bluetooth_on 0

# Verify Bluetooth state
adb shell settings get global bluetooth_on