An information disclosure vulnerability exists in the way that the Microsoft Server Message Block 1.0 (SMBv1) server handles certain requests. An attacker who successfully exploited this vulnerability could craft a special packet, which could lead to information disclosure from the server.
To exploit the vulnerability, in most situations, an unauthenticated attacker could send a specially crafted packet to a targeted SMBv1 server.
The security update addresses the vulnerability by correcting how SMBv1 handles these specially crafted requests.
For customers running Windows Vista and later See Microsoft Knowledge Base Article 2696547.
Alternative method for customers running Windows 8.1 or Windows Server 2012 R2 and later For client operating systems:
For server operating systems:
Impact of workaround. The SMBv1 protocol will be disabled on the target system.
How to undo the workaround. Retrace the workaround steps, and select the SMB1.0/CIFS File Sharing Support check box to restore the SMB1.0/CIFS File Sharing Support feature to an active state.