Internet Key Exchange (IKE) version 1 protocol, as implemented on Cisco IOS, VPN 3000 Concentrators, and PIX firewalls, allows remote attackers to cause a denial of service (resource exhaustion) via a flood of IKE Phase-1 packets that exceed the session expiration rate. NOTE: it has been argued that this is due to a design weakness of the IKE version 1 protocol, in which case other vendors and implementations would also be affected.

Multiple cross-site scripting (XSS) vulnerabilities in the WebVPN feature in the Cisco VPN 3000 Series Concentrators and Cisco ASA 5500 Series Adaptive Security Appliances (ASA), when in WebVPN clientless mode, allow remote attackers to inject arbitrary web script or HTML via the domain parameter in (1) dnserror.html and (2) connecterror.html, aka bugid CSCsd81095 (VPN3k) and CSCse48193 (ASA). NOTE: the vendor states that "WebVPN full-network-access mode" is not affected, despite the claims by the original researcher.

Cisco VPN 3000 Concentrator before 4.1.7.F allows remote attackers to determine valid groupnames by sending an IKE Aggressive Mode packet with the groupname in the ID field, which generates a response if the groupname is valid, but does not generate a response for an invalid groupname.

Cisco VPN 3000 series Concentrator running firmware 4.1.7.A and earlier allows remote attackers to cause a denial of service (device reload or drop user connection) via a crafted HTTPS packet.