ageet AGEphone before 1.6.2, running on Windows Mobile 5 on the HTC HyTN Pocket PC device, allows remote attackers to (1) cause a denial of service (call disruption and device hang) via a SIP message with a malformed header and (2) cause a denial of service (call disruption, false ring indication, and device outage) via a SIP message with a malformed SDP delimiter.