Cisco IP phones (7941, 7961, 7911, 7906) with the latest firmwares do not accept the Accept-Language Header field (blocking unknown or wrong headers helps blocking buffer overflow or similar attacks) and answer with a 'SIP/2.0 406 Not Acceptable', while the Accept-Language Header field is supported in other messages (REGISTER for instance).
This has been seen on SIP firmwares from 8.5 to 8.0.
Does anyone have any experiance with this issue or know of a workaround?
