Software Engineering Institute

The Microsoft Server Message Block (SMB), and its follow-on, Common Internet File System (CIFS), are network protocols that Windows uses to share files, printers, serial ports, and communicate between computers. A vulnerability exists in the way that the affected operating systems validate certain incoming SMB packets. Additional details about the underlying cause of the vulnerability are not known.

An unauthenticated remote attacker may be able to exploit this vulnerability by sending specially-crafted SMB packets to a vulnerable system. Microsoft reports that this vulnerability may also be exploited through a malicious web page. In this scenario, an attacker would need to trick or persuade a user into browsing the malicious web page or following a link to the malicious web page provided in an email message.

A remote, unauthenticated attacker could execute arbitrary code on a vulnerable system.

Apply a patch

Microsoft has published MS05-011 in response to this issue. Users are strongly encouraged to review this bulletin and apply the patches it refers to.

Workarounds

Filter network traffic
Microsoft Security Bulletin MS05-011 also contains recommendations about packet filtering to mitigate this issue. Users, particularly those who are affected but unable to apply the patches, are encouraged to implement these workarounds.