iDefense Security Advisory 03.23.06: RealNetworks RealPlayer and Helix Player Invalid Chunk Size Heap Overflow Vulnerability


RealNetworks RealPlayer and Helix Player Invalid Chunk Size Heap Overflow Vulnerability iDefense Security Advisory 03.23.06 http://www.idefense.com/intelligence/vulnerabilities/display.php?id=404 March 23, 2006 I. BACKGROUND RealPlayer is an application for playing various media formats, developed by RealNetworks Inc. For more information, visit http://www.real.com/. II. DESCRIPTION Remote exploitation of a heap-based buffer overflow in RealNetwork Inc's RealPlayer could allow the execution of arbitrary code in the context of the currently logged in user. The vulnerability specifically exists in the handling of the 'chunked' Transfer-Encoding method. This method breaks the file the server is sending up into 'chunks'. For each chunk, the server first sends the length of the chunk in hexadecimal, followed by the chunk data. This is repeated until there are no more chunks. The server then sends a chunk length of 0 indicating the end of the transfer. There are multiple ways of triggering this vulnerability. * Sending a well-formed chunk header with a length of -1 (FFFFFFFF) followed by malicious data. * Sending a well-formed chunk header with a length specified which is less than the amount of data that will be sent, followed by malicious data. * Not sending a chunk header before sending malicious data. Each of these cases result in a heap overflow. Depending on the versions used, certain of these cases will not cause exploitable issues. However, the last case appears to be reliable in triggering a crash. III. ANALYSIS Successful exploitation allows a remote attacker to execute arbitrary code with the privileges of the currently logged in user. In order to exploit this vulnerability, an attacker would need to entice a user to follow a link to a malicious server. Once the user visits a website under the control of an attacker, it is possible in a default install of RealPlayer to force a web-browser to use RealPlayer to connect to an arbitrary server, even when it is not the default application for handling those types, by the use of embedded object tags in a webpage. This may allow automated exploitation when the page is viewed. As the client sends its version information as part of the request, it would be possible for an attacker to create a malicious server which uses the appropriate offsets and shellcode for each version and platform of the client. IV. DETECTION iDefense has confirmed the existence of this vulnerability in RealPlayer Version 10.4 and 10.5 for Windows and Both RealPlayer 10.4 and Helix Player 1.4 for Linux. The vendor has stated that the following versions are vulnerable: * RealPlayer 10.5 ( * RealPlayer 10 * RealOne Player v2 * RealOne Player v1 * RealPlayer 8 It is suspected that previous versions of RealPlayer and Helix Player are affected by this vulnerability. V. WORKAROUND Although there is no way to completely protect yourself from this vulnerability, aside from removing the RealPlayer software, the following actions may be taken to minimize the risk of automated exploitation. Disable ActiveX controls and plugins, if not necessary for daily operations, using the following steps: 1. In IE, click on Tools and select Internet Options from the drop-down menu. 2. Click the Security tab and the Custom Level button. 3. Under ActiveX Controls and Plugins, then Run Activex Controls and Plugins, click the Disable radio button. In general, exploitation requires that a targeted user be socially engineered into visiting a link to a server controlled by an attacker. As such, do not visit unknown/untrusted website and do not follow suspicious links. When possible, run client software, especially applications such as IM clients, web browsers and e-mail clients, from regular user accounts with limited access to system resources. This may limit the immediate consequences of client-side vulnerabilities such as this. VI. VENDOR RESPONSE Information from the vendor about this vulnerability is available at to following URL: http://service.real.com/realplayer/security/03162006_player/en/ VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CAN-2005-2922 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 09/08/2005 Initial vendor notification 09/09/2005 Initial vendor response 03/23/2006 Public disclosure IX. CREDIT This vulnerability was found internally by Greg MacManus of iDefense Labs. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp Free tools, research and upcoming events http://labs.idefense.com X. LEGAL NOTICES Copyright (c) 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 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.