Dynamic VPN Configuration Protocol service (DVCP) in Watchguard Firebox firmware 5.x.x allows remote attackers to cause a denial of service (crash) via a malformed packet containing tab characters to TCP port 4110.
The PPTP VPN service in Watchguard Firebox before 10, when performing the MS-CHAPv2 authentication handshake, generates different error codes depending on whether the username is valid or invalid, which allows remote attackers to enumerate valid usernames.