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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2004.0714 -- iDEFENSE Security Advisory 11.08.04 Samba SMBD Remote Denial of Service Vulnerability 9 November 2004 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Samba 3.0.x to 3.0.7 Publisher: iDEFENSE Operating System: Linux variants UNIX variants Mac OS X Impact: Denial of Service Access: Existing Account CVE Names: CAN-2004-0930 Original Bulletin: http://www.idefense.com/application/poi/display?id=156 - --------------------------BEGIN INCLUDED TEXT-------------------- Samba SMBD Remote Denial of Service Vulnerability iDEFENSE Security Advisory 11.08.04 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: http://www.samba.org/samba/ftp/patches/security/samba-3.0.7-CAN-2004-093 0.patch 3.0.7 patch signature: http://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 (http://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 http://www.idefense.com/poi/teams/vcp.jsp X. LEGAL NOTICES Copyright (c) 2004 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any 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. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBQZAVsSh9+71yA2DNAQKVvQP/fS/DO4lzO9Ob6r5XmckUMK33mIyDWz+a 9osPJ6iCSDCFIcEMZtAwNPrpD1fV3XvLCy03F3DGbiyhOnXnkvqImb5KJSzmVDjb BaUB3DQDrIzPeGsL9s23S6279pwP+zTBc7SJ6L/RVS1jMcfHQ1Hh5eedi6qKQbx1 7A1vyyeY9YU= =xMWM -----END PGP SIGNATURE-----