By issuing various invalid OBEX messages to the phone’s protocol handler it is possible to trigger one of several Denial of Service vulnerabilities. This attack results in the phone resetting, terminating any current operations. No device pairing is required therefore anyone in range of the phone could initiate an attack.
This was verified and tested on a Nokia 6310i, but will probably work with other Nokia phones as well, as they use the same protocol handler. Nokia has confirmed the vulnerability.
I may be overly cynical here, but resets and lock-ups as a result of bluetooth activity are nothing too special with Nokia phones. It took Nokia more than two years to come up with a decent firmware version for the Nokia 6310i (i.e. one that would sync with a wide range of bluetooth adaptors, not just with Nokia’s own), and even the Series 60 devices behave funny in connection with PCs (reporting errors when pairing or connecting to BT serial ports).
Update: More on this from ZDnet, Slashdot and TechDirt – Thanks Jim!