Microsoft Windows SMB NULL Session Authentication

high Nessus Plugin ID 26920
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VPR Score: 5.8


It is possible to log into the remote Windows host with a NULL session.


The remote host is running Microsoft Windows. It is possible to log into it using a NULL session (i.e., with no login or password).

Depending on the configuration, it may be possible for an unauthenticated, remote attacker to leverage this issue to get information about the remote host.


Apply the following registry changes per the referenced Technet advisories :
Set :
- HKLM\SYSTEM\CurrentControlSet\Control\LSA\RestrictAnonymous=1
- HKLM\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters\restrictnullsessaccess=1

Reboot once the registry changes are complete.

See Also

Plugin Details

Severity: High

ID: 26920

File Name: smb_null_session.nasl

Version: 1.35

Type: remote

Agent: windows

Family: Windows

Published: 10/4/2007

Updated: 9/2/2020

Dependencies: smb_login.nasl

Risk Information

Risk Factor: High

VPR Score: 5.8

CVSS Score Source: CVE-2019-0519

CVSS v2.0

Base Score: 7.5

Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS v3.0

Base Score: 7.3

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Vulnerability Information

CPE: cpe:/o:microsoft:windows

Required KB Items: SMB/null_session_enabled

Vulnerability Publication Date: 7/14/1999

Reference Information

CVE: CVE-1999-0519, CVE-1999-0520, CVE-2002-1117

BID: 494