A new security vulnerability, CVE-2025-22435, has been identified in the AVRCP Bluetooth implementation, specifically in the avdt_msg_ind function found in avdt_msg.cc. This flaw allows remote attackers to achieve memory corruption due to a type confusion bug, which could result in privilege escalation for already paired Bluetooth devices—all without requiring user interaction or additional permissions.

This post explains, in simple terms, what this vulnerability is, how it works, and why you should care, even if you’re just an end user.

What Is Type Confusion?

Type confusion happens when a program uses one type of data as if it were a different type. In C++ codebases, this often lets an attacker change how much memory gets read or written, corrupting memory, creating new bugs, or making privileged actions possible.

Where’s the Problem?

The broken code lives in the Bluetooth stack, in the file avdt_msg.cc within the avdt_msg_ind function. This function handles incoming Bluetooth Audio/Video Distribution Transport Protocol (AVDTP) messages from paired devices.

Here’s a simplified version of the problematic pattern

// avdt_msg.cc
void avdt_msg_ind(void* p_msg) {
    avdt_msg *msg = (avdt_msg*)p_msg;

    // Type confusion occurs here if 'p_msg' is not really an 'avdt_msg'
    if (msg->type == AVDT_MSG_TYPE_DISCOVER) {
        process_discover_msg(msg);
    } else if (msg->type == AVDT_MSG_TYPE_GET_CAP) {
        process_get_cap_msg(msg);
    }
    // ... other branches
}

What’s wrong?
If an attacker sends a crafted Bluetooth packet, they can trick the function into treating something that isn’t an avdt_msg as though it is. That’s the type confusion, which leads to out-of-bounds accesses or writing to memory they shouldn’t touch.

Attacker gets Bluetooth pairing (they already have a trusted relationship).

2. Attacker sends a malformed packet that tricks avdt_msg_ind into reading/writing as the wrong type.

Memory corruption happens, possibly controlling sensitive parts of memory.

4. Privilege escalation: The attacker may now do things reserved for the system or higher privileged processes, like grabbing protected Bluetooth data, injecting malicious data, or disabling security checks.

No extra permissions and no user interaction is necessary—which means if you’re paired with a malicious device, you’re vulnerable as soon as you’re in range.

Proof-of-Concept Exploit

Below is conceptual pseudo-code showing exploitation. (The real attack code depends on the platform and Bluetooth stack version.)

# Pseudo Python - PoC idea
import bluetooth

target_address = 'XX:XX:XX:XX:XX:XX'  # Replace with victim MAC

# Create a crafted payload with a falsified type field
malicious_packet = b'\xDE\xAD\xBE\xEF' + b'\x00'*100  # Replace with real fuzzed packet

sock = bluetooth.BluetoothSocket(bluetooth.L2CAP)
sock.connect((target_address, x0019))  # AVDTP signaling channel

# Send malicious packet to trigger vulnerability
sock.send(malicious_packet)
sock.close()

Stealing sensitive blueooth data

- Tampering with audio/video data streams

How to Stay Safe

- Update your device: New firmware/OS patches fix this issue.

Unpair suspicious Bluetooth devices.

- Monitor Bluetooth connections for odd/unknown activity.

References & Further Reading

- CVE-2025-22435 MITRE Entry
- Android Security Bulletin, June 2025 (see "Bluetooth vulnerabilities")
- Bluetooth SIG Security Notices
- Example discussion: Type Confusion in Bluetooth stacks (old)

Conclusion

CVE-2025-22435 is a dangerous bug: it enables privilege escalation on devices you thought were safe, just because they’re paired with the wrong Bluetooth device and don’t require your say-so to take over. If your phone, speaker, or laptop vendor pushes a firmware update soon—take it! Disable pairing with unknown gadgets, and be Bluetooth-cautious.

Timeline

Published on: 09/02/2025 23:15:34 UTC
Last modified on: 09/04/2025 16:38:05 UTC