Cisco Virtual Private Network (VPN) Client software 2.x.x, and 3.x before 3.5.1C, does not properly verify that certificate DN fields match those of the certificate from the VPN Concentrator, which allows remote attackers to conduct man-in-the-middle attacks.

VPN Server module in Linksys EtherFast BEFVP41 Cable/DSL VPN Router before 1.40.1 reduces the key lengths for keys that are supplied via manual key entry, which makes it easier for attackers to crack the keys.

Cisco VPN 5000 series concentrator hardware 6.0.21.0002 and earlier, and 5.2.23.0003 and earlier, when using RADIUS with a challenge type of Password Authentication Protocol (PAP) or Challenge, sends the user password in cleartext in a validation retry request, which could allow remote attackers to steal passwords via sniffing.

Buffer overflow in the vpnclient program for UNIX VPN Client before 3.5.2 allows local users to gain administrative privileges via a long profile name in a connect argument.

CIPE VPN package before 1.3.0-3 allows remote attackers to cause a denial of service (crash) via a short malformed packet.

Check Point VPN-1 4.1SP4 using SecuRemote returns different error messages for valid and invalid users, with prompts that vary depending on the authentication method being used, which makes it easier for remote attackers to conduct brute force attacks.

Nokia Firewall Appliances running IPSO 3.3 and VPN-1/FireWall-1 4.1 Service Pack 3, IPSO 3.4 and VPN-1/FireWall-1 4.1 Service Pack 4, and IPSO 3.4 or IPSO 3.4.1 and VPN-1/FireWall-1 4.1 Service Pack 5, when SYN Defender is configured in Active Gateway mode, does not properly rewrite the third packet of a TCP three-way handshake to use the NAT IP address, which allows remote attackers to gain sensitive information.

Buffer overflow in the GUI authentication code of Check Point VPN-1/FireWall-1 Management Server 4.0 and 4.1 allows remote attackers to execute arbitrary code via a long user name.

Format string vulnerability in Check Point VPN-1/FireWall-1 4.1 allows a remote authenticated firewall administrator to execute arbitrary code via format strings in the control connection.

Check Point VPN-1/FireWall-1 4.1 base.def contains a default macro, accept_fw1_rdp, which can allow remote attackers to bypass intended restrictions with forged RDP (internal protocol) headers to UDP port 259 of arbitrary hosts.

Cisco VPN 3000 series concentrators before 2.5.2(F) allow remote attackers to cause a denial of service via an IP packet with an invalid IP option.

Cisco VPN 3000 series concentrators before 2.5.2(F) allow remote attackers to cause a denial of service via a flood of invalid login requests to (1) the SSL service, or (2) the telnet service, which do not properly disconnect the user after several failed login attempts.

Check Point VPN-1/FireWall-1 4.1 SP2 with Fastmode enabled allows remote attackers to bypass access restrictions via malformed, fragmented packets.

Check Point VPN-1/FireWall-1 4.1 and earlier allows remote attackers to bypass the directionality check via fragmented TCP connection requests or reopening closed TCP connection requests, aka "One-way Connection Enforcement Bypass."

Check Point VPN-1/FireWall-1 4.1 and earlier improperly retransmits encapsulated FWS packets, even if they do not come from a valid FWZ client, aka "Retransmission of Encapsulated Packets."

The inter-module authentication mechanism (fwa1) in Check Point VPN-1/FireWall-1 4.1 and earlier may allow remote attackers to conduct a denial of service, aka "Inter-module Communications Bypass."

The OPSEC communications authentication mechanism (fwn1) in Check Point VPN-1/FireWall-1 4.1 and earlier allows remote attackers to spoof connections, aka the "OPSEC Authentication Vulnerability."

The seed generation mechanism in the inter-module S/Key authentication mechanism in Check Point VPN-1/FireWall-1 4.1 and earlier allows remote attackers to bypass authentication via a brute force attack, aka "One-time (s/key) Password Authentication."

Buffer overflow in Getkey in the protocol checker in the inter-module communication mechanism in Check Point VPN-1/FireWall-1 4.1 and earlier allows remote attackers to cause a denial of service.

Check Point VPN-1/FireWall-1 4.1 and earlier allows remote attackers to redirect FTP connections to other servers ("FTP Bounce") via invalid FTP commands that are processed improperly by FireWall-1, aka "FTP Connection Enforcement Bypass."