Title: ====== Skype Community - Mail Encoding Web Vulnerability #1
Date: ===== 2012-11-20 References: =========== http://www.vulnerability-lab.com/get_content.php?id=708 MICROSOFT SECURITY RESPONSE CENTER (MSRC) ID: [13021bc] VL-ID: ===== 708 Common Vulnerability Scoring System: ==================================== 3.5 Introduction: ============= Skype is a proprietary voice-over-Internet Protocol service and software application originally created in 2003 by Swedish entrepreneur Niklas Zennström and his Danish partner Janus Friis. It has been owned by Microsoft since 2011. The service allows users to communicate with peers by voice, video, and instant messaging over the Internet. Phone calls may be placed to recipients on the traditional telephone networks. Calls to other users within the Skype service are free of charge, while calls to landline telephones and mobile phones are charged via a debit-based user account system. Skype has also become popular for its additional features, including file transfer, and videoconferencing. Competitors include SIP and H.323-based services, such as Linphone, as well as the Google Talk service, Mumble and Hall.com. Skype has 663 million registered users as of September 2011. The network is operated by Microsoft, which has its Skype division headquarters in Luxembourg. Most of the development team and 44% of the overall employees of the division are situated in Tallinn and Tartu, Estonia. Unlike most other VoIP services, Skype is a hybrid peer-to-peer and client–server system. It makes use of background processing on computers running Skype software. Skype`s original proposed name (Sky Peer-to-Peer) reflects this fact. Some network administrators have banned Skype on corporate, government, home, and education networks, citing reasons such as inappropriate usage of resources, excessive bandwidth usage, and security concerns. (Copy of the Vendor Homepage: http://en.wikipedia.org/wiki/Skype) Abstract: ========= The Vulnerability Laboratory Research Team discovered a filter & mail encoding vulnerability in the official Skype Community Website Application. Report-Timeline: ================ 2012-09-28: Researcher Notification & Coordination 2012-09-30: Vendor Notification 2012-10-02: Vendor Response/Feedback 2012-11-18: Vendor Fix/Patch 2012-11-21: Public or Non-Public Disclosure Status: ======== Published Affected Products: ================== Microsoft Product: Community (Forums) 2012 Q3-4 Exploitation-Technique: ======================= Remote Severity: ========= Medium Details: ======== A filter and mail encoding vulnerability is detected in the official Skype Community Website Application. The vulnerability is located in the not sanitized message body and title parameters when processing to load the bound vulnerable Problem Reporter or Send to Friends module. The vulnerability affects the later outgoing mails service and allows execution of persistent script codes against admins, moderators or customers of the forum. The script code get executed out of the message itself inside of the main mail template. Successful exploitation of the vulnerabilities result in persistent phishing mails, persistent session hijacking attacks and persistent mail web context manipulation via skype website. Vulnerable Section(s): [+] Skype Community (Forums) Vulnerable Module(s): [+] Problem Reporter & Send to Friends Vulnerable Parameter(s): [+] Message Body & Title (says) Affected: [+] Notification Mail (outgoing) Proof of Concept: ================= The vulnerability can be exploited by remote attackers with low or medium required user inter action and with skype application service user account. For demonstration or reproduce ... Send to Friends: http://community.skype.com/t5/notifications/notifymoderatorpage/message-uid/1062818 http://community.skype.com/t5/notifications/emailmessagepage/board-id/de_computer_windows/message-id/6304 Problem Reporter: http://community.skype.com/t5/notifications/notifymoderatorpage/message-uid/1075268 Support: https://support.skype.com/de/support_request_form?needsLogin=true&topic=6270000000026383241&problem=6270000000028975692 PoC: <html><head> <title>Einladung zum Besuch bei Skype Support Network</title> <link rel="important stylesheet" href="chrome://messagebody/skin/messageBody.css"> </head> <body> <table class="header-part1" border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr> <td><b>Betreff: </b>Einladung zum Besuch bei Skype Support Network</td></tr><tr><td><b>Von: </b> rm01x <[email protected]></td></tr><tr><td><b>Datum: </b>Tue, 25 Sep 2012 15:32:34 -0700 (PDT) </td></tr></tbody></table><table class="header-part2" border="0" cellpadding="0" cellspacing="0" width="100%"><tbody><tr><td><b>An: </b>01x445 <[email protected]></td></tr></tbody></table><br> <title> Einladung zum Besuch bei Skype Support Network </title> rm01x ([email protected]) bei Skype Support Network findet es faszinierend, hilfreich, interessant, nützlich, provozierend, zum Nachdenken anregend oder einfach cool. Wir hoffen, Sie besuchen Skype Support Network und schauen es sich mit eigenen Augen an. <p> <a href="http://community.skype.com/skypec/board/message?board.id=de_computer_windows &message.id=6304#M6304">http://community.skype.com/skypec/board/message?board. id=de_computer_windows&message.id=6304#M6304</a> </p> <p> rm01x sagt: </p> <p> >"<[PERSISTENT INJECTED MALICIOUS SCRIPT CODE!]/"> Note: The attacker can send the code via `send to friends` to hijack customer accounts or via problem reporter to a moderator or administrator of the skype community. The script code will be executed directly out of the unsanitized message body of the mail. The vulnerability also exists in the skype main server when requesting via automatically help or contact forms. The outgoing mail with the malicious script code as values can be send to users/customers or to the moderator/administrator. Solution: ========= The vulnerability can be patched by parsing the message context of the send to friends or problem reporter module. Restrict the input forms of the contact or problem report formulars [A-Z][a-z][0-9] to remove the attack vector. Risk: ===== The security risk of the filter encoding and validation vulnerability is estimated as medium(+). Credits: ======== Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected]) Disclaimer: =========== The information provided in this advisory is provided as it is without any warranty. Vulnerability-Lab disclaims all warranties, either expressed or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability- Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss of business profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. 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