Cisco Virtual Private Network (VPN) Client software 2.x.x, and 3.x before 3.5.2B, does not generate sufficiently random numbers, which may make it vulnerable to certain attacks such as spoofing.

Unspecified vulnerability in the VPN Client for Windows Graphical User Interface (GUI) (aka the VPN client dialer) in Cisco VPN Client for Windows 4.8.00. and earlier, except for 4.7.00.0533, allows local authenticated, interactive users to gain privileges, possibly due to privileges of dialog boxes, aka bug ID CSCsd79265.

Cisco Virtual Private Network (VPN) Client 3.5.4 and earlier allows remote attackers to cause a denial of service (CPU consumption) via a packet with a zero-length payload.

Buffer overflows in Cisco Virtual Private Network (VPN) Client 3.5.4 and earlier allows remote attackers to cause a denial of service via (1) an Internet Key Exchange (IKE) with a large Security Parameter Index (SPI) payload, or (2) an IKE packet with a large number of valid payloads.

Multiple cross-site scripting (XSS) vulnerabilities in (1) PreSearch.html and (2) PreSearch.class in Cisco Secure Access Control Server (ACS), VPN Client, Unified Personal Communicator, MeetingPlace, Unified MeetingPlace, Unified MeetingPlace Express, CallManager, IP Communicator, Unified Video Advantage, Unified Videoconferencing 35xx products, Unified Videoconferencing Manager, WAN Manager, Security Device Manager, Network Analysis Module (NAM), CiscoWorks and related products, Wireless LAN Solution Engine (WLSE), 2006 Wireless LAN Controllers (WLC), and Wireless Control System (WCS) allow remote attackers to inject arbitrary web script or HTML via the text field of the search form.

The StartServiceCtrlDispatcher function in the cvpnd service (cvpnd.exe) in Cisco VPN client for Windows before 5.0.06.0100 does not properly handle an ERRORFAILEDSERVICECONTROLLERCONNECT error, which allows local users to cause a denial of service (service crash and VPN connection loss) via a manual start of cvpnd.exe while the cvpnd service is running.