Cisco Security Advisory – Devices running Cisco IOS versions 12.0S, 12.2, 12.3 or 12.4 and configured for Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs) or VPN Routing and Forwarding Lite (VRF Lite) and using Border Gateway Protocol (BGP) between Customer Edge (CE) and Provider Edge (PE) devices may permit information to propagate between VPNs. Workarounds are available to help mitigate this vulnerability.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/70317/cisco-sa-20080924-vpn.txt
Source: https://packetstormsecurity.com/files/70317/Cisco-Security-Advisory-20080924-vpn.html