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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2010.0686.2 Citrix ICA Client ActiveX Memory Corruption Vulnerabillity 12 August 2010 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Citrix ICA Client Publisher: iDEFENSE Operating System: Windows UNIX variants (UNIX, Linux, OSX) Impact/Access: Execute Arbitrary Code/Commands -- Remote with User Interaction Resolution: Patch/Upgrade CVE Names: CVE-2010-2990 CVE-2010-2991 Original Bulletin: http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=875 Revision History: August 12 2010: Added CVE references August 5 2010: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- iDefense Security Advisory 08.03.10 http://labs.idefense.com/intelligence/vulnerabilities/ Aug 03, 2010 I. BACKGROUND The Citrix ICA Client is an ActiveX control used to connect to a Citrix XenApp (formerly Citrix Presentation Server) server via the browser. Using this control allows clients to access the various features provided by the application server, such as virtualized applications. For more information, see the vendor's site found at the following link. http://www.citrix.com/English/ss/downloads/results.asp?productID=186&c1=sot2755 II. DESCRIPTION Remote exploitation of a memory corruption vulnerability in Citrix Systems Inc.'s ICA Client could allow an attacker to execute arbitrary code with the privileges of the current user. The vulnerability occurs in the IICAClient interface within the ICAClient library in the control. This is the primary interface used to implement the client's functionality. The vulnerability occurs in a certain function, which is accessible through JavaScript. This function is responsible for reading a remote ICA (Independent Computing Architecture# file from the server. Typically, the contents of this file are used to provide options controlling the connection to the application gateway. During the reading of this file, the vulnerable function fails to check the return value of the realloc## function. It then adds the number of bytes read from the file so far to the value returned, and appends file data at this address. If this allocation fails, a NULL pointer #the value 0) will be returned. This results in "0 + the number of bytes read so far" being used as the destination address for writing file data. This can lead to the corruption of memory at that address, which results in the execution of arbitrary code. III. ANALYSIS Exploitation of this vulnerability results in the execution of arbitrary code with the privileges of the user viewing the web page. To exploit this vulnerability, a targeted user must load a malicious webpage created by an attacker. An attacker typically accomplishes this via social engineering or injecting content into compromised, trusted sites. After the user visits the malicious web page, no further user interaction is needed. IV. DETECTION iDefense has confirmed the existence of this vulnerability in ICA Client versions 12.0.0.6410 and 11.2.0.31560. All versions of the Online Plug-in for Windows up to version 12.0.3. V. WORKAROUND Setting the KillBit for the CLSID containing the vulnerable control will prevent exploitation of this vulnerability. However, it will also prevent legitimate use of the control. The CLSID is: 238F6F80-B8B4-11CF-8771-00A024541EE3 VI. VENDOR RESPONSE Citrix has released a patch which addresses this issue. Information about downloadable vendor updates can be found by clicking on the URLs shown. http://citrix.com/English/ss/downloads/details.asp?downlaodld=2301299&productId=186 VII. CVE INFORMATION A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet. VIII. DISCLOSURE TIMELINE 04/06/2010 Initial Contact 04/07/2010 Initial Response 08/03/2010 Coordinated public disclosure. IX. CREDIT This vulnerability was discovered by Sean Larsson, iDefense Labs. Get paid for vulnerability research http://labs.idefense.com/methodology/vulnerability/vcp.php Free tools, research and upcoming events http://labs.idefense.com/ X. LEGAL NOTICES Copyright © 2010 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 e-mail 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 =========================================================================== 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 iD8DBQFMY5V8/iFOrG6YcBERAmFJAJ9k0Cl4pHTwAyDeOfZb1gUwNGKmrQCg3hu/ l0yVtZ3ZWLbY00yTSM3K/iU= =BsjR -----END PGP SIGNATURE-----