In FreeBSD 12.0-STABLE before r350637, 12.0-RELEASE before 12.0-RELEASE-p9, 11.3-STABLE before r350638, 11.3-RELEASE before 11.3-RELEASE-p2, and 11.2-RELEASE before 11.2-RELEASE-p13, the bsnmp library is not properly validating the submitted length from a type-length-value encoding. A remote user could cause an out-of-bounds read or trigger a crash of the software such as bsnmpd resulting in a denial of service.
https://security.netapp.com/advisory/ntap-20190910-0002/
https://security.FreeBSD.org/advisories/FreeBSD-SA-19:20.bsnmp.asc
https://seclists.org/bugtraq/2019/Aug/6
http://packetstormsecurity.com/files/153959/FreeBSD-Security-Advisory-FreeBSD-SA-19-20.bsnmp.html