This indicates an attempt to exploit a buffer-overflow vulnerability in the Now SMS MMS Gateway web interface.
The vulnerability is caused by a boundary error when the vulnerable software handles a long Authorization header. It allows a remote attacker to execute arbitrary code via sending a crafted HTTP request.
Now SMS/MMS Gateway 2007.06.26 and earlier.
System Compromise: Remote attackers can gain control of vulnerable systems.
Update to version 2008.02.22 or higher, available from the following web site.