The remote host is missing an update to the system as announced in the referenced advisory FreeBSD-SA-06:18.ppp.asc

Upgrade your system to the appropriate stable release or security branch dated after the correction date https://secure1.securityspace.com/smysecure/catid.html?in=FreeBSD-SA-06:18.ppp.asc

The ppp(4) driver implements the Point-to-Point Protocol for using serial lines (e.g., modems) as network interfaces. While processing Link Control Protocol (LCP) configuration options received from the remote host, ppp(4) fails to correctly validate option lengths. This may result in data being read or written beyond the allocated kernel memory buffer.