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Samba 3.x SMBD Remote Denial of Service Vulnerability

09.13.04

BACKGROUND

Samba is a software suite that provides file and print services to
SMB/CIFS clients, such as Microsoft Windows platforms. For more
information see:

http://www.samba.org/

DESCRIPTION

An unauthenticated remote user can cause a resource exhaustion attack by
sending multiple malformed requests to an affected server. Each request
spawns a new process, which enters an infinite loop.

ANALYSIS

This attack takes very little bandwidth to cause the machine to stop
responding. Each request from the exploit tested was only 358 bytes, and
a Redhat Fedora Core 1 machine with 512 megabytes of RAM and 512
megabytes of swap took fewer than 4000 requests to render it unusable.

DETECTION

iDEFENSE has confirmed Samba 3.0.2 and 3.0.4 are vulnerable.

The vendor has confirmed that Samba 3.0.x prior to and including v3.0.6
are vulnerable.

WORKAROUND

Restricting access to the server by using the "hosts allow" setting in
smb.conf and/or applying firewall rules may help mitigate this
vulnerability.

VENDOR RESPONSE

The patch file for Samba 3.0.5 addressing [the] bug
(samba-3.0.5-DoS.patch) can be downloaded from:

   http://download.samba.org/samba/ftp/patches/security/

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2004-0807 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

09/02/2004    Initial vendor notification
09/02/2004    iDEFENSE clients notified
09/02/2004    Vendor response
09/13/2004    Coordinated public disclosure

CREDIT

The discoverer wishes to remain anonymous.

Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp

LEGAL NOTICES

Copyright © 2004 Verisign, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
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part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.