This indicates an attempt to exploit a denial of service vulnerability in the SIP channel driver (channels/chan_sip.c) in Asterisk.
The vulnerability in the SIP channel driver (channels/chan_sip.c) can be exploited to cause the creation of "a real pvt structure" that uses more resources than necessary. This allows remote attackers to cause a denial of service.
Asterisk 1.2.x before 1.2.13 and 1.4.x before 1.4.0-beta3.
Denial of Service.
Update to "net-misc/asterisk-1.2.13" or later.