Software Engineering Institute

SMB and the Common Internet File System (CIFS) are closely related protocols used sharing data and resources between computers. According to Microsoft, "CIFS is an enhanced version of Microsoft's open, cross-platform Server Message Block (SMB) protocol." Windows uses this protocol to share files, printers, serial ports, and to communicate between computers using named pipes and mail slots.

Microsoft's implementation of SMB does not properly validate the size of incoming SMB packets. An remote attacker with valid credentials on the server could use this vulnerability to execute arbitrary code or cause a denial of service on a vulnerable system. For more information ,see Microsoft Security Bulletin MS03-024.

An authenticated remote attacker may be able to exploit this vulnerability to run arbitrary code on the system or cause a denial of service with the privileges of the vulnerable service.

Apply a patch from Microsoft as described in Microsoft Security Bulletin MS03-024.

If a patch can't be applied, or as a workaround until a patch can be applied, you can block ports TCP/139 and TCP/445 and UDP/139 and UDP/445 at your network perimeter. This will still leave you exposed to attacks inside your network. Additionally, you may wish to block these ports using a host-based firewall, such as Microsoft's Internet Connection Firewall (ICF) or a similar product available from a number of vendors.