Document Title: =============== Skype 2.8.x & 5.3.x - Memory Corruption Vulnerability References (Source): ==================== http://www.vulnerability-lab.com/get_content.php?id=180 CNNVD-201110-710 > http://www.cnnvd.org.cn/vulnerability/show/cv_id/2011100710 Release Date: ============= 2011-08-22 Vulnerability Laboratory ID (VL-ID): ==================================== 180 Product & Service Introduction: =============================== Skype is a famous software application that allows users to make voice and video calls and chats over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system. Skype has also become popular for its additional features which include instant messaging, file transfer, and videoconferencing. Skype has 663 million registered users as of 2010. The network is operated by Skype Limited, which has its headquarters in Luxembourg. In 2011 Microsoft bought the skype company & the software is now a official microsoft product. (Copy of the website: http://en.wikipedia.org/wiki/Skype) Abstract Advisory Information: ============================== Vulnerability-Lab team discovered a memory corruption vulnerability on the Skype VoIP v5.3.x, v2.8.x & v5.1.x software. Vulnerability Disclosure Timeline: ================================== 2011-07-02: Vendor Notification 2011-07-04: Vendor Response/Feedback 2011-07-24: Vendor Fix/Patch 2011-08-22: Public or Non-Public Disclosure Discovery Status: ================= Published Affected Product(s): ==================== Microsoft Corp. Product: Skype - Software Client 5.3.x 2.2.x 5.2.x Exploitation Technique: ======================= Local Severity Level: =============== Medium Technical Details & Description: ================================ A critical pointer vulnerability is located in the macosx & windows version of skype. The bug/vulnerability is located in 2 input forms of an uni-code http search request to the skype search directory server. The vulnerability allows an local attacker to crash the complete skype process via an unknown unhandled software exception(memory-corruption). Successful exploitation of the bug can lead to local system compromise by overwriting on a machine specific memory address. Vulnerable Module(s): [+] Input Mask - Geschäftsempfehlungen finden - Wo? & Was? Verified on OS: [+] Windows [+] MacOS [+] Linux Affected OS version(s): Windows v5.3.0.120 & older versions MacOS v5.2.0.1523 & older versions Ubuntu v2.2.0.35 & older versions Debian v2.2.0.35-1 & older versions Fedora v2.2.0.35-f & older versions Suse v2.2.0.35-s & older versions Pictures: ../1.png ../2.png ../skype_debug_win7_x64x.png ../skype_debug2_win7_x64x.png ../skype_error_mac_osx_x64x.tiff ../unhandled-exception_win7_x64.png Proof of Concept (PoC): ======================= The vulnerability can be exploited by local attackers. For demonstration or reproduce ... Manually reproduce ... 1. Install Skype Software 2. Register an Account 3. Login & switch to the search Menu "Geschäftsempfehlungen finden - Wo? & Was?" 4. Include a emtpy long zero-string or a long uni-code string like AAAAAAAAA+ on the input mask (1.png) 5. Switch to immunity or windbg & catch the process (skype_debug_win7_x64x.png) 6. Execute the input of the mask ... & feel free (1.png) 7. An unhandled & unknown exception get droped and the software crashs via memory-corruption by an pointer bug 7. Read & write after local exploitation like ... skype_debug2_win7_x64x.png ... is possible :) Analyses: ../debug_log_win7.txt Solution - Fix & Patch: ======================= 2011-07-24: Vendor Fix/Patch - Skype decided to exclude the skype user directory Security Risk: ============== The security risk of the local exploitable memory corruption vulnerability is estimated as medium. Credits & Authors: ================== Vulnerability Research Laboratory - Benjamin Kunz Mejri (Rem0ve) Disclaimer & Information: ========================= 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. 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