A vulnerability in the Transmission Control Protocol (TCP) specification (RFC793) has been discovered by an external researcher. The successful exploitation enables an adversary to reset any established TCP connection in a much shorter time than was previously discussed publicly. Depending on the application, the connection may get automatically re-established. In other cases, a user will have to repeat the action (for example, open a new Telnet or SSH session). Depending upon the attacked protocol, a successful attack may have additional consequences beyond terminated connection which must be considered. This attack vector is only applicable to the sessions which are terminating on a device (such as a router, switch, or computer), and not to the sessions that are only passing through the device (for example, transit traffic that is being routed by a router). In addition, the attack vector does not directly compromise data integrity or confidentiality.
All Cisco products which contain a TCP stack are susceptible to this vulnerability.
This advisory is available at
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20040420-tcp-nonios["http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20040420-tcp-nonios"], and it describes this vulnerability as it applies to Cisco products that do not run Cisco IOS® software.
A companion advisory that describes this vulnerability for products that run Cisco IOS software is available at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20040420-tcp-ios["http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20040420-tcp-ios"].