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- -------------------------------------------------------------------
SySS-Advisory: Grandstream Budge Tone 101/102 DoS Vulnerability
- -------------------------------------------------------------------

Problem discovered: July 20th 2005
Vendor contacted: July 21th 2005
Advisory will published on: August 12th 2005

AUTHOR: Pierre Kroma (kroma@syss.de)
SySS GmbH
72070 Tuebingen / Germany
Tel.: +49-7071-407856-0
Key fingerprint =3D 927A B13E 16F5 BBAB 8F17 75EB D8E1 A9A4 F257 4EEC

DEVICE: Grandstream Budge Tone-101
Grandstream Budge Tone-102
AFFECTED VERSIONS: perhaps all(?) <=3D 1.0.6.7 (firmware 1.0.6.7 tested)

EXPLOIT: attached
VENDOR STATUS: informed
SEVERITY: medium
Remotely exploitable: yes

DESCRIPTION:
It is possible to initiate a D.o.S attack against this voip
(hardware-)phone. If you send an UDP packet greater than 65534 bytes=20
to port 5060 the device stops working:

- any active telephone call will be aborted.
- the display will show nothing / display freeze.
- the integrated HTTP-server won't be reachable any more.

To solve the problem, you must switch the phone off and on again.

If you send a packet of exactly 65534 bytes the device may reboot.
Smaller packets have no effect.

################################################## ##########################
EXAMPLE:
Grandstream BT101/BT102 DoS
written by pierre kroma (kroma@syss.de)

ping the remote device xxx.xxx.xxx.xxx
PING xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx) 56(84) bytes of data.
64 bytes from xxx.xxx.xxx.xxx: icmp_seq=3D1 ttl=3D250 time=3D0.479 ms
64 bytes from xxx.xxx.xxx.xxx: icmp_seq=3D2 ttl=3D250 time=3D0.406 ms
64 bytes from xxx.xxx.xxx.xxx: icmp_seq=3D3 ttl=3D250 time=3D0.404 ms

--- xxx.xxx.xxx.xxx ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev =3D 0.404/0.429/0.479/0.042 ms

Wait ...

ping the remote device xxx.xxx.xxx.xxx again
PING xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx) 56(84) bytes of data.

--- xxx.xxx.xxx.xxx ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 1999ms
################################################## ##########################

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