Cisco Systems warned today of a serious flaw affecting routers used primarily by universities and local dial-up ISPs. The flaw affects Firewall Authentication Proxy for FTP and/or Telnet services and could expose affected routers to denial-of-service (DoS) attacks and execution of arbitrary code. The Cisco advisory includes patches and workarounds (depending on which Cisco IOS software is used). This firewall authentication flaw is not related to an earlier flaw reported in Cisco routers that was made famous at this year's Black Hat.