firewall
In the zone
Samba SMBD Remote Denial of Service Vulnerability
-----
Code:
www.idefense.com/application/poi/display?id=156&type=vulnerabilities
November 08, 2004
I. BACKGROUND
Samba is an Open Source/Free Software suite that provides seamless file
and print services to SMB/CIFS clients.
II. DESCRIPTION
Remote exploitation of an input validation error in Samba could allow an
attacker to consume system resources and potentially cause the target
system to crash.
The problem specifically exists within the ms_fnmatch() routine which
upon parsing '*' characters within a pattern will fall into an
exponentially growing loop. The responsible section of vulnerable code
appears here:
case '*':
for (; *n; n++) {
if (ms_fnmatch(p, n) == 0) return 0;
}
break;
An authenticated remote attacker can cause a resource exhaustion attack
by sending multiple malformed commands to an affected server. A request
as simple as 'dir ***********************************************z' can
trigger this condition leading to 100% CPU usage.
III. ANALYSIS
Successful exploitation allows authenticated remote attackers to exhaust
CPU resources. This attack takes very little bandwidth and can, in some
cases, cause the machine to stop responding. Multiple attacks can be
launched in parallel which can make this attack more effective.
IV. DETECTION
iDEFENSE has confirmed the existence of this vulnerability in Samba
versions 3.0.4 and 3.0.7. It is suspected that all versions of Samba up
to and including 3.0.7 are vulnerable.
V. 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.
VI. VENDOR RESPONSE
3.0.7 patch:
*www.samba.org/samba/ftp/patches/security/samba-3.0.7-CAN-2004-093
0.patch
3.0.7 patch signature:
*www.samba.org/samba/ftp/patches/security/samba-3.0.7-CAN-2004-093
0.patch.asc
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2004-0930 to these issues. This is a candidate for inclusion
in the CVE list (*cve.mitre.org), which standardizes names for
security problems.
VIII. DISCLOSURE TIMELINE
09/29/2004 iDEFENSE clients notified
09/29/2004 Initial vendor notification
09/30/2004 Initial vendor response
11/08/2004 Coordinated public disclosure
IX. CREDIT
Karol Wiesek is credited with this discovery.
Get paid for vulnerability research
*www.idefense.com/poi/teams/vcp.jsp
X. LEGAL NOTICES
Copyright (c) 2004 iDEFENSE, Inc.-----
