The IOS improperly verifies user credentials within the FTP server, Cisco said in an advisory. Remote attackers could exploit this to "bypass the authentication process and retrieve or write any file from the device file system (including the configuration file)," the networking giant added. Also, an error in the FTP server surfaces when certain files are transferred. Remote attackers could use the error to cause a vulnerable device to reload, creating a denial-of-service condition.
The flaws affect Cisco IOS versions 11.3, 12.0, 12.1, 12.2, 12.3 and 12.4.
However, the IOS FTP server is an optional service disabled by default, Cisco noted. Devices that are not specifically configured to enable the IOS FTP server service are unaffected by the flaws.