A denial of service vulnerability exists in the Microsoft Server Block Message (SMB) when an attacker sends specially crafted requests to the server. An attacker who exploited this vulnerability could cause the affected system to stop responding until it is manually restarted. To attempt to exploit this issue, an attacker would need to send specially crafted SMB requests to the target system.
Note that the denial of service vulnerability would not allow an attacker to execute code or to elevate their user rights, but it could cause the affected system to stop accepting requests.
The security update addresses the vulnerability by correcting the manner in which SMB handles specially crafted client requests.