CVE-2025-5479

Executive Summary

CVE-2025-5479 is a critical heap-based buffer overflow vulnerability in the Bluetooth AVCTP protocol implementation of the Sony XAV-AX8500 car stereo system. An attacker who can pair a malicious Bluetooth device with the target system can trigger remote code execution (RCE) in the context of the current process. The vulnerability stems from improper validation of user-supplied data length before copying it to a heap buffer. With a CVSS score of 7.5, this flaw poses a significant risk to vehicle infotainment systems, potentially allowing attackers to execute arbitrary code, manipulate audio, or pivot to other vehicle networks. No public exploit or patch is currently available, but the vulnerability is weaponizable through Bluetooth proximity attacks.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary embedded system (Sony XAV-AX8500) and does not involve open-source software supply chains.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector: Adjacent Network (Bluetooth)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (pairing)
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: High. Exploitation requires physical proximity and Bluetooth pairing, but once achieved, full code execution is possible.

Deep Dive & Mechanics

The vulnerability resides in the Bluetooth AVCTP (Audio/Video Control Transport Protocol) implementation of the Sony XAV-AX8500. AVCTP is used for remote control of audio/video devices over Bluetooth. The specific flaw is a heap-based buffer overflow triggered when the device processes a crafted AVCTP packet with an oversized length field.

Technical Flow:

1. An attacker pairs a malicious Bluetooth device (e.g., a smartphone or custom Bluetooth adapter) with the Sony XAV-AX8500.
2. The attacker sends a specially crafted AVCTP packet containing a length field that exceeds the allocated heap buffer size.
3. The device copies the user-supplied data into the heap buffer without proper validation, causing a buffer overflow.
4. The overflow corrupts adjacent heap memory, allowing the attacker to overwrite function pointers or other critical data.
5. This leads to arbitrary code execution in the context of the AVCTP process (likely running with system privileges).

Root Cause: Lack of bounds checking on the length field in the AVCTP packet handler. The code likely uses memcpy or similar without verifying that the source length does not exceed the destination buffer size.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is inferred from the CVE description. A typical vulnerable implementation might look like:

// Vulnerable code (pseudo)
void handle_avctp_packet(uint8_t *packet, uint16_t length) {
    uint8_t buffer[256];
    // No length validation
    memcpy(buffer, packet, length); // Heap overflow if length > 256
}

A patched version would include length validation:

// Patched code (pseudo)
void handle_avctp_packet(uint8_t *packet, uint16_t length) {
    uint8_t buffer[256];
    if (length > sizeof(buffer)) {
        // Reject oversized packet
        return;
    }
    memcpy(buffer, packet, length);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A Bluetooth-capable device (e.g., Raspberry Pi with Bluetooth adapter)
• Python with pybluez or similar library
• Target: Sony XAV-AX8500 in pairing mode

Exploit Steps:

1. Pair the attacker device with the Sony XAV-AX8500 (requires user interaction on the stereo).
2. Send a crafted AVCTP packet with an oversized length field to trigger the heap overflow.
3. Use heap spraying or other techniques to achieve code execution.

Example Python script (conceptual):

import bluetooth

target_addr = "XX:XX:XX:XX:XX:XX"  # Target Bluetooth MAC
sock = bluetooth.BluetoothSocket(bluetooth.RFCOMM)
sock.connect((target_addr, 1))  # AVCTP typically uses RFCOMM channel 1

# Craft malicious AVCTP packet
# Header: 2 bytes (AVCTP header)
# Length field: 2 bytes (set to overflow value)
# Payload: shellcode or ROP chain
packet = b"\x00\x10"  # AVCTP header
packet += b"\xFF\xFF"  # Oversized length (65535)
packet += b"A" * 300  # Overflow data

sock.send(packet)
sock.close()

Note: No public exploit code is available; this is a conceptual example.

Blue Team

Detection:

• Monitor Bluetooth pairing events and AVCTP packet sizes.
• Look for unusually large AVCTP packets (length > 256 bytes).
• Use network monitoring tools to capture Bluetooth traffic.

Honeypot Setup:

• Deploy a Sony XAV-AX8500 in a controlled environment.
• Log all Bluetooth connections and AVCTP packets.
• Alert on oversized packets or repeated pairing attempts.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Bluetooth packets with AVCTP length field > 256 bytes
  • Repeated pairing attempts from unknown devices
  • Unusual RFCOMM connections on channel 1

• Host IOCs:

  • Unexpected process crashes or restarts on the Sony XAV-AX8500
  • Heap memory corruption logs (if available)
  • Unauthorized Bluetooth device MAC addresses in pairing history

• File IOCs:

  • Modified firmware binaries (if attacker gains persistence)
  • Suspicious files in /tmp or /data partitions

Detection Engineering

YARA Rule

rule CVE_2025_5479_AVCTP_Overflow {
    meta:
        description = "Detects oversized AVCTP packets targeting Sony XAV-AX8500"
        author = "Valters IT"
        date = "2025-04-01"
        cve = "CVE-2025-5479"
    strings:
        $avctp_header = { 00 10 }  // AVCTP header bytes
        $large_length = { FF FF }  // Length field > 256
    condition:
        $avctp_header at 0 and $large_length at 2
}

Sigma Rule

title: CVE-2025-5479 Bluetooth AVCTP Heap Overflow
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects oversized AVCTP packets in Bluetooth traffic
author: Valters IT
logsource:
    category: network_connection
    product: bluetooth
detection:
    selection:
        protocol: "RFCOMM"
        channel: 1
        packet_length: > 256
    condition: selection
falsepositives:
    - Legitimate large AVCTP packets (unlikely)
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-5479 Bluetooth AVCTP Heap Overflow"; flow:to_server; content:"|00 10|"; offset:0; depth:2; content:"|FF FF|"; offset:2; depth:2; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Bluetooth on the Sony XAV-AX8500 if not required.
2. Avoid pairing with untrusted Bluetooth devices.
3. Monitor for firmware updates from Sony.

Long-term Fix:

• Sony must release a firmware patch that adds proper length validation in the AVCTP handler.
• Implement input sanitization and bounds checking for all Bluetooth protocol handlers.

Workarounds:

• Use a Bluetooth firewall or filter to block oversized packets.
• Restrict Bluetooth pairing to authorized devices only.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.