Microsoft Windows SMB NULL Session Authentication

Medium Nessus Plugin ID 26920


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

Remove BROWSER from :
- HKLM\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters\NullSessionPipes

Reboot once the registry changes are complete.

See Also

Plugin Details

Severity: Medium

ID: 26920

File Name: smb_null_session.nasl

Version: $Revision: 1.30 $

Type: remote

Agent: windows

Family: Windows

Published: 2007/10/04

Modified: 2012/02/29

Dependencies: 10394

Risk Information

Risk Factor: Medium


Base Score: 5

Temporal Score: 4.2

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:N

Temporal Vector: CVSS2#E:U/RL:U/RC:ND

Vulnerability Information

Required KB Items: SMB/null_session_enabled

Exploit Available: false

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 1999/07/14

Reference Information

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

BID: 494

OSVDB: 299, 8230