VoIP Phones - Cisco 7xxx
Phones and Versions Tested
|Cisco 7xxx Versions tested|
|7940G||SIP41.9-4-2SR1-1S||Phone runs sluggish, reboots randomly, not recommended|
|Supports 302 Redirect||?|
|Tested on FireBrick SIP Server||Yes|
* Important *
Whilst testing SIP41.8-5-4S it appears the phone/firmware is vulnerable to a SIP/UDP amplification attack where crafted SIP 'INVITE' packets sent on UDP 5600 cause the phone to respond to its upstream SIP gateway with multiple SIP 2.0 '404' packets. Measured at a rate of approximately 20 packets/second, whilst not a major cause for concern with a single phone could potentially cause service issues where several phones are in use.
This vulnerability is protected against by correct firewall protection/filtering limiting inbound UDP on SIP port 5600 to the phone to be exclusively from the parent SIP service (e.g. voiceless.aa.net.uk - see the VoIP security/firewall section). It is not recommended to leave these phones connected to the internet without any protection.