Bluetooth is everywhere – in our headphones, smartphones, TVs, cars. It feels as reliable and as safe as the air we breathe. But sometimes, serious bugs slip through. In 2024, a newly discovered flaw was found in Bluetooth’s GATT (Generic Attribute Profile) server implementation, which could let an attacker write outside the boundaries of memory, and potentially run code on a victim device. This security hole is tracked as CVE-2024-49747.

Let’s break down what’s really happening, why this is so dangerous, and, if you’re a developer or security enthusiast, see how the vulnerable code looks and how attackers might exploit it.

What Is GATT and Where’s the Problem?

The Generic Attribute Profile (GATT) is a set of rules for Bluetooth communications. It handles how two Bluetooth Low Energy devices send information back and forth. One device acts as the "server," another as "client." The server holds information in a table; the client reads or writes to the table via requests.

Inside Android’s Bluetooth stack, the code that answers a client’s "read request" is handled by a function called gatts_process_read_by_type_req in a file named gatt_sr.cc.

Due to a logic mistake, that function doesn’t always check its memory access properly. If attacked, it may write data beyond where it’s supposed to – a so-called out-of-bounds write. Hackers love these bugs because out-of-bounds writes often let them control or crash target devices.

Let’s peek at the (simplified) vulnerable code section

void gatts_process_read_by_type_req(...) {
    ... // Other code
    for (size_t i = ; i < num_handles; i++) {
        // Calculate where in the response buffer to write
        size_t offset = calculate_offset(i);

        // Oops! No check that 'offset' is in bounds
        memcpy(&response_buffer[offset], handle_value, value_length); 
    }
    ... // Other code
}

How is This Exploited?

An attacker (nearby, with Bluetooth access) sends a crafted GATT Read By Type request that tricks the server into calculating a bogus offset. Since the code doesn’t check the buffer boundaries, it writes where it shouldn’t.

For example, let’s say calculate_offset(i) goes haywire and gives an offset that’s beyond response_buffer size. That lets a hacker inject data into other parts of memory, which in some cases means they can insert code to be run (aka remote code execution).

No user action is needed. Just leaving Bluetooth on is enough for an attack to work on a vulnerable device.

Simple Exploit Demo (Conceptual)

> Note: This won’t crash your system; real exploitation is much more complex and risky! This is to show how requests can be used shape memory access.

A python exploit might look like

import bluetooth

# Connect to device
target_addr = "XX:XX:XX:XX:XX:XX"
port = x001  # GATT usually on PSM 1 or similar

# Construct a GATT Read By Type request with oversized attributes
payload = b'\x08' + b'\x00\x01\xFF\xFF'  # Example, not real
# Send it using a vulnerable Bluetooth library implementation
sock = bluetooth.BluetoothSocket(bluetooth.L2CAP)
sock.connect((target_addr, port))
sock.send(payload)
sock.close()

This shows how you’d send a malformed read request. On a vulnerable server, this could trigger the bug and the out-of-bounds write.

Possibly smart TVs, IoT gadgets, some cars, and embedded devices using the affected code.

No special privileges are needed. Just being nearby and able to send Bluetooth packets is enough.

How Bad Is It, Really?

- Remote Code Execution: An attacker could potentially run any code they like, such as malware, spyware, etc.

References and Fixes

- Google Android Security Bulletin, June 2024
- CVE Details: CVE-2024-49747
- AOSP gatt_sr.cc Source

Patch: The fix is simple in concept – check that each offset remains within the bounds of response_buffer before writing. Always validate buffer sizes before writing, and apply official security updates!

Quick Summary

CVE-2024-49747 is a bug in the Bluetooth GATT server code (gatts_process_read_by_type_req in gatt_sr.cc), causing an out-of-bounds write that hackers can exploit for remote code execution. If you’re using an Android phone or device with Bluetooth, keep your software updated, and if you’re a developer, make sure to review and patch your code accordingly.

Bluetooth is a vital modern tool, but like all tech, it needs careful maintenance. Don’t let invisible risks linger – keep updated, and spread the word about CVE-2024-49747.

Timeline

Published on: 01/21/2025 23:15:15 UTC
Last modified on: 01/22/2025 15:15:13 UTC