Description
Within some Nortel products, notable the MCS 5100, UNIStim File Transfer Protocol (UFTP) is used. UFTP is a proprietary file transfer protocol, which is transported over UNIStim control channel over Reliable UDP. Due to flaws within the handling of UFTP messages it is possible to cause a number of different Denial of Service (DoS) attacks against the affected equipment by manipulating values in Connection Details fields.
Recommendations
Nortel has acknowledge the issue and is working on correcting it. One of the variations of this vulnerability is already addressed in MCS version 3.5.9. More details can be found in Nortel SECURITY ADVISORY BULLETIN, 2008009103, Rev 1 at http://support.nortel.com/go/main.jsp?cscat=BLTNDETAIL&id=774845. Nortel customers with a valid support agreement may wish to speak with their support contact in order to obtain additional vendor details. In the short term it is recommended that a VoIP aware IPS product, such as VoIPguard, with signatures to detect unatuthorized attempts to access system resources using the hardcoded accounts be implemented to prevent them from being exploited. In addition, implementation of general best practice guidance such as controlling access to telephony networks via VLAN’s, access control lists, firewalls, network admission controls and/or other security devices will aid in limiting the exposure of this vulnerability.