This is the user process PPP package as found in FreeBSD and OpenBSD. Normally, PPP is implemented as a part of the kernel (e.g., as managed by pppd(8)) and it's thus somewhat hard to debug and/or modify its behaviour. However, in this implementation PPP is done as a user process with the help of the tunnel device driver (tun).
Binary packages can be installed with the high-level tool pkgin (which can be installed with pkg_add) or pkg_add(1) (installed by default). The NetBSD packages collection is also designed to permit easy installation from source.
The pkg_admin audit command locates any installed package which has been mentioned in security advisories as having vulnerabilities.
Please note the vulnerabilities database might not be fully accurate, and not every bug is exploitable with every configuration.
Problem reports, updates or suggestions for this package should be reported with send-pr.