Server Message Block†servers contain a vulnerability in the default Guest account login that could allow an unauthenticated, remote attacker to gain user privileges to view or modify files and gain control of the affected system.
Server Message Block (SMB) is a protocol for sharing files, printers, serial ports, and communications abstractions, such as named pipes and mail slots between computers.† Microsoft Windows operating systems utilize SMB server implementations.
Since SMB servers have a default Guest account, an unauthenticated, remote attacker attempting to login with an unrecognized account name will be logged in as "Guest."† An exploit could allow the attacker to gain user privileges to view or modify files and gain control of the affected system.
Administrators are advised to disable all Guest accounts on local workstations and servers and domain controllers and to limit privileges to trusted users.
The security vulnerability applies to the following combinations of products.
Security Activity Bulletin
Original Release Base
The urgency and severity ratings of this alert are not tailored to individual users; users may value alerts differently based upon their network configurations and circumstances. THE ALERT, AND INFORMATION CONTAINED THEREIN, ARE PROVIDED ON AN "AS IS" BASIS AND DO NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE ALERT, AND INFORMATION CONTAINED THEREIN, OR MATERIALS LINKED FROM THE ALERT, IS AT YOUR OWN RISK. INFORMATION IN THIS ALERT AND ANY RELATED COMMUNICATIONS IS BASED ON OUR KNOWLEDGE AT THE TIME OF PUBLICATION AND IS SUBJECT TO CHANGE WITHOUT NOTICE. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.