This indicates an attack attempt to exploit a Security Bypass vulnerability in Cisco AnyConnect VPN client.
The vulnerability is due to a lack of validation when handling the vpndownloader.exe program. An attacker can exploit this by tricking an unsuspecting user into visiting a malicious webpage, allowing the attacker to downgrade the software to a previous version which is vulnerable to other exploits.
Cisco Systems AnyConnect Secure Mobility Client 2.x prior to 2.5.6005
Cisco Systems AnyConnect Secure Mobility Client 3.0.x prior to 3.0.08057
System Compromise: Remote attackers can gain control of vulnerable systems.
Security Bypass: Remote attackers can bypass security checking of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.