Title: ====== Skype Community - Mail Encoding Web Vulnerability #2
Date: ===== 2012-11-21 References: =========== http://www.vulnerability-lab.com/get_content.php?id=719 VL-ID: ===== 719 Common Vulnerability Scoring System: ==================================== 4 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: ================ 2012-10-08: Researcher Notification & Coordination 2012-10-10: Vendor Notification 2012-10-12: Vendor Response/Feedback 2012-11-18: Vendor Fix/Patch 2012-11-21: Public or Non-Public Disclosure Status: ======== Published Affected Products: ================== Microsoft Product: Skype Community - Lithium Forums 2012 Q3 Exploitation-Technique: ======================= Remote Severity: ========= High Details: ======== A persistent input validation vulnerability is detected in the official Skype Community Website Application. The vulnerability is located in the update post form with the unsanitized username in send mails. Attackers can inject malicious persistent script code on application side of the skype skype community. The vulnerability is located in the filter function of the username when skype community is processing to send a not parsed update mail. Remote attacker with low privileged application user accounts can change the username values to malicious persistent script code via POST. The result in a persistent script code inject via [email protected]. Successful exploitation of the vulnerability result in persistent phishing attacks, persistent session hijacking or mail context manipulation via persistent inject. Vulnerable Section(s): [+] Skype Community - (Forums) Vulnerable Module(s): [+] Notification Mail Vulnerable Parameter(s): [+] Username Affected Section(s): [+] Update Mail - Filter / Output Listing Proof of Concept: ================= The vulnerability can be exploited by remote attackers with low privileged application user account and with low or medium required user inter action. For demonstration or reproduce ... <html> <head> <title>Skype Support Network Subscription: 1 Update: Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich durch die Accounts</title> <link rel="important stylesheet" href="chrome://messagebody/skin/messageBody.css"> </head> <body> <table border=0 cellspacing=0 cellpadding=0 width="100%" class="header-part1"><tr><td><b>Betreff: </b>Skype Support Network Subscription: 1 Update: Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich durch die Accounts</td></tr><tr><td><b>Von: </b>Community Mailer <[email protected]></td></tr><tr><td><b>Datum: </b>06.10.2012 16:04</td></tr></table><table border=0 cellspacing=0 cellpadding=0 width="100%" class="header-part2"><tr> <td><b>An: </b>rm01x <[email protected]></td></tr></table><br> <html> <head> <title> Skype Support Network Subscription: 1 Update: Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich durch die Accounts </title> <style type="text/css"> body, td { font: 10pt Arial, Helvetica; } </style> </head> <body class="lia-body email-template"> <div class="lia-content subscription subscription-digest"> <div class="email-header"> <h2 class="email-greeting"> Hello <[[PERSISTENT INJECTED SCRIPT CODE AS USERNAME!]]>, </h2> <p class="email-totals"> You have 1 update for your Skype Support Network Subscriptions. </p> </div><!-- end email-header --> <div class="email-main email-subscriptions"> <hr /> <div class="email-subscription"> <h3>Subscription to Thema: <a href="http://community.skype.com/t5/Skype-f%C3%BCr-Windows/Skype-is-Hacked-Win32- Trojan-Agent-Gen-schleicht-sich-durch-die/td-p/1086370">Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich durch die Accounts</a> (1 Update)</h3> <div class="email-subscription-notifications"> <div class="email-subscription-notification"> There was a new Antworten.<br> <table class="notification-metadata" border=0 cellspacing=0 cellpadding=2> <tr><td>Subject: </td><td> <a href="http://community.skype.com/t5/Skype-f%C3%BCr-Windows/Skype-is-Hacked-Win32- Trojan-Agent-Gen-schleicht-sich-durch-die/m-p/1101468#M6531">Betreff: Skype is Hacked ! Win32.Trojan.Agent.Gen schleicht sich durch die Accounts</a></td></tr> <tr><td>Author:</td><td>Methu (New Member)</td></tr> <tr><td>Date:</td><td>06-10-2012 16:04</td></tr> </table> <p class="email-notification-body-separate"> <a href="http://community.skype.com/t5/Skype-f%C3%BCr-Windows/Skype-is-Hacked-Win32-Trojan-Agent-Gen- schleicht-sich-durch-die/m-p/1101468#M6531">View</a> </p> </div><!-- end email-subscription-notification --> </div><!-- end email-subscription-notifications --> </div><!-- end email-subscription --> </div><!-- end email-subscriptions --> <hr /> <div class="email-footer"> <p class="manage-normal"> To manage your subscriptions or to change your subscription options, click <a href="http://community.skype.com/skypec/user_subscriptions";>here</a>. </p> <p class="manage-alternate"> If this link doesn't work: <ol> <li>Log on to Skype Support Network.</li> <li>Click <b>My Profile</b>.</li> <li>Click the <b>Subscriptions & Bookmarks</b> tab. </li> <li>Change your settings and click <b>Save Changes</b>. </li> </ol> </p> <p class="manage-thanks">Thanks for being a Skype Support Network member.</p> <p class="manage-team"> <i>Your Skype Support Network Team</i> </p> <font size=-1> <p class="manage-sent-to"> Skype Support Network sent this message to [email protected]. </p> <p class="manage-unsubscribe"> Did not request this email yourself? Click <a href="http://community.skype.com/t5/user/RemoveUserEmailPage/user-id /1915382/mail-message-tracking/H7YSNPPZVRU0CL">this link</a> to permanently prevent your email address being used on our community (NB: You won't be able to use the address yourself in the future). </p> </font> </div><!-- end email-subscriptions-manage --> </div><!-- end lithium-content --> </body> </html> </body> </html> Solution: ========= The vulnerability can be patched by parsing the context with the lithium api request of the community application formular. Risk: ===== The security risk of the filter & mail encoding vulnerability is estimated as medium(+)|(-)high. 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. 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