26zl Bluetooth Classic (BR/EDR) Attacks
Older than BLE, less commonly attacked today, but still present in cars, industrial sensors, audio gear, and legacy enterprise hardware. Many of the well-known historic attacks (BlueSnarf, BlueBug) are mitigated; KNOB and the BlueBorne family remain relevant against unpatched devices.
Quick Workflow
- Discover devices with
hcitool/bluetoothctl/redfang - Enumerate exposed services via SDP
- Test each service profile for unauth access
- Check pairing crypto (KNOB applicability)
- Proximity-physical attacks for legacy / unpatched
Discovery
# Modern adapter (built-in or USB Bluetooth 4.0+)
sudo hciconfig hci0 up
sudo hcitool inq # inquiry
sudo hcitool scan --length=12 # 12-second scan
# bluetoothctl interactive
bluetoothctl
> scan on
> devices
# Discoverable-mode-only devices appear; non-discoverable need address brute
sudo redfang -r 00:00:00:00:00:00-FF:FF:FF:FF:FF:FF
# (very slow — ~7 hours per OUI prefix)
Service Discovery (SDP)
# List all services on a device
sdptool browse AA:BB:CC:DD:EE:FF
sdptool records AA:BB:CC:DD:EE:FF
Common profiles and their attack relevance:
| Profile | UUID | Attack |
|---|---|---|
| OBEX Object Push (OPP) | 0x1105 | BlueSnarf/BlueBug on legacy phones (mostly extinct) |
| OBEX File Transfer (FTP) | 0x1106 | Browse / write filesystem on legacy devices |
| Headset (HSP/HFP) | 0x1108 / 0x111E | Eavesdrop active call audio |
| Serial Port Profile (SPP) | 0x1101 | Industrial/IoT debug ports — often unauthenticated |
| HID | 0x1124 | Keyboard/mouse impersonation |
| Audio Sink/Source (A2DP) | 0x110B / 0x110A | Audio injection/eavesdrop |
SPP Abuse
The Serial Port Profile (SPP) tunnels arbitrary data over Bluetooth as a virtual COM port. Industrial / IoT devices use it for debug or telemetry, often without authentication.
# Connect to SPP service, channel typically 1
sudo rfcomm bind /dev/rfcomm0 AA:BB:CC:DD:EE:FF 1
sudo screen /dev/rfcomm0 9600
# Then interact with the device's CLI / debug menu
KNOB (CVE-2019-9506)
Forces Bluetooth pairing to negotiate a 1-byte encryption key — making the link key trivially brute-forceable.
# Test with internalblue (requires Broadcom firmware patch)
git clone https://github.com/seemoo-lab/internalblue
internalblue
> log keys
# Patch firmware to allow 1-byte key; pair with target; observe weak key
Patched in firmware on most modern devices. Still works against:
- Older Broadcom-based devices (pre-2019 BCM chipsets)
- Embedded automotive Bluetooth stacks
- Cheap consumer audio gear
BlueBorne (CVE-2017-1000251 et al.)
A family of buffer overflows / info leaks in major Bluetooth stacks (Linux BlueZ, Android, Windows, iOS). Mostly patched 2017–2018, but unpatched embedded Linux devices are common.
# Armis blueborne-scanner — checks for patch-level
git clone https://github.com/ArmisSecurity/blueborne
python blueborne_scanner.py AA:BB:CC:DD:EE:FF
HID Spoofing (PoC)
If pairing succeeds via Just Works or weak PIN, you can register as a HID device — keystroke injection on an unattended Bluetooth-paired host.
# bdaddr + HID example — register custom HID on rfcomm
hcitool dev
hciconfig hci0 class 0x000540 # HID device class
sdptool add HID
# Use a HID descriptor crafted as keyboard, send keystrokes
Audio Eavesdropping
If a target has Bluetooth headset paired and active, and you can re-pair (PIN brute or KNOB):
- HSP/HFP profiles let you become the peer and receive audio
- Some firmware allows simultaneous peer connections — eavesdrop without disrupting
Engagement Cheatsheet
# 1. Discover
sudo hcitool inq
# 2. Enumerate services per device
sdptool browse <MAC>
# 3. SPP (industrial/IoT) — connect and explore
sudo rfcomm bind /dev/rfcomm0 <MAC> 1
sudo screen /dev/rfcomm0 9600
# 4. Patch-level scan
python blueborne_scanner.py <MAC>
# 5. KNOB testing (with adapter that supports internalblue)
internalblue → log keys → re-pair target
# 6. Document profiles, auth state, exposed commands per device
Detection
- No native Bluetooth Classic IDS in most environments
- Active inquiry visible to nearby Bluetooth-aware monitoring (rare)
- Re-pairing prompts on target devices may surface to users
Reporting
- Identify chipset + firmware version per device (often visible in service records)
- Map CVE applicability (BlueBorne, KNOB, BlueFrag, et al.)
- Document specific profile abuses (SPP exposed without auth, HID spoofing successful, etc.)
Key References
- internalblue: github.com/seemoo-lab/internalblue
- KNOB attack: knobattack.com
- BlueBorne: armis.com/blueborne
- Bluetooth Core Spec — Volume 2 (BR/EDR Controller)
- Source: https://github.com/SnailSploit/offensive-checklist/blob/main/wireless.md