14 September 2006
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2006.0662 -- [UNIX/Linux] Multiple Vendor X Server CID-keyed Fonts 'scan_cidfont()' Integer Overflow Vulnerability 14 September 2006 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: XFree86 X.Org Publisher: iDEFENSE Operating System: UNIX variants (UNIX, Linux, OSX) Impact: Root Compromise Execute Arbitrary Code/Commands Access: Existing Account CVE Names: CVE-2006-3740 Original Bulletin: http://www.idefense.com/intelligence/vulnerabilities/display.php?id=411 - --------------------------BEGIN INCLUDED TEXT-------------------- Multiple Vendor X Server CID-keyed Fonts 'scan_cidfont()' Integer Overflow Vulnerability iDefense Security Advisory 09.12.06 http://www.idefense.com/intelligence/vulnerabilities/ Sep 12, 2006 I. BACKGROUND The X Window System is a graphical windowing system based on a client/server model. More information about about The X Window system is available at the following link: http://en.wikipedia.org/wiki/X_Window_System II. DESCRIPTION Local exploitation of an integer overflow vulnerability in the 'scan_cidfont()' function in the X.Org and XFree86 X server could allow an attacker to execute arbitrary code with privileges of the X server, typically root. The vulnerability specifically exists in the handling of 'CMap' and 'CIDFont' font data. When parsing this information no checks are made that the count of items for the 'begincodespacerange', 'cidrange' and 'notdefrange' sections. In addition to a 'standard' integer overflow, the implementation of 'vm_alloc()' makes it possible to overwrite memory before the allocated region. III. ANALYSIS Successful local exploitation allows an attacker to execute arbitrary as the root user. In order to exploit this vulnerability an attacker would require the ability to send commands to an affected X server. This typically requires access to the console, or access to the same account as a user who is on the console. One method of gaining the required access would be to remotely exploit a vulnerability in, for example, a graphical web browser. This would then allow an attacker to exploit this vulnerability and elevate their privileges to root. IV. DETECTION iDefense has confirmed the existence of this vulnerability in the X.org server version 6.8.2. Analysis of the source code for the current versions of the X.org and XFree86 servers indicates that current versions of both are vulnerable. Previous versions may also be affected. V. WORKAROUND Access to the vulnerable code can be prevented by removing the entry for the Type1 font module from your Xservers configuration file, often stored in /etc/X11 and named xorg.conf or XF86Config-4. To do this, remove the following line from the 'Module' section: Load "type1" This will prevent Type 1 fonts from loading, which may affect the appearance or operation of some applications. VI. VENDOR RESPONSE The X.Org foundation has addressed this vulnerability with libXfont version 1.2.1. Additionally, patches have been made available for older releases. " The XFree86 Project Inc. is making available a source patch available at ftp://xfree86.org/pub/XFree86/4.6.0/fixes/fix-01 that, in part, addresses this vulnerability. " VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2006-3740 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 08/25/2006 Initial vendor notification 08/25/2005 Initial vendor response (X.Org) 09/10/2006 Initial vendor response (XFree86) 09/12/2006 Coordinated public disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. Get paid for vulnerability research http://www.idefense.com/methodology/vulnerability/vcp.php Free tools, research and upcoming events http://labs.idefense.com/ X. LEGAL NOTICES Copyright Â© 2006 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 firstname.lastname@example.org 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 email@example.com 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: firstname.lastname@example.org 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 iQCVAwUBRQjiWih9+71yA2DNAQL0ugP/TvTfyRbhm/K0Fb66yJ2AYGImOJ6Ko/Wm f1s8Mnj5Cj8AyUvUKTY5T0+sJiIjSeOUjYXZVqOtF9URBb0bunZpiOj7aYV7Mwiz 4vp1ohyFqtf6DtAZAt/822Ay1HeKhWi2x6Jhzy/aymbwvugw2+jpNk5kzVAlk7EM RXDDiPF6kLE= =66go -----END PGP SIGNATURE-----