The (1) fwdrv.sys and (2) khips.sys drivers in Sunbelt Kerio Personal Firewall 4.3.268 and earlier do not validate arguments passed through to SSDT functions, including NtCreateFile, NtDeleteFile, NtLoadDriver, NtMapViewOfSection, NtOpenFile, and NtSetInformationFile, which allows local users to cause a denial of service (crash) and possibly other impacts via unspecified vectors.

The FWDRV driver in Kerio Personal Firewall 4.2 and Server Firewall 1.1.1 allows local users to cause a denial of service (crash) by setting the PAGENOACCESS or PAGEGUARD protection on the Page Environment Block (PEB), which triggers an exception, aka the "PEB lockout vulnerability."