Firmware upgrade for all
Linksys has released firmware version 1.45.11, dated June 4, that specifically mentions closing the BOOTP and memory leak hole which allowed remote sniffing of TCP/IP traffic passing through the devices.
Here is a quick list of fixes, straight from the release notes:
Fixed CGI string attacks issue
Fixed UPnP on Windows XP SP2 issue
Fixed One way audio issue
Fixed NAT-T issue for some VPN connection
Fixed DHCP server revision, fill the siaddr to the server address
Fixed DHCP (BOOTP) vulnerability issue
Added Filter IDENT(port 113) to appear stealth when scanned
Added DHCP option 55 support
Fixed buffer leakage bug
Modified TCP Support RFC 3360 standard
Modified PPPoE/L2TP/PPTP fragmentation supports fragmenting 1 packet into more than 3.
Modified MTU/MRU function for better handling
News source: The Inquirer