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Skype Account Service - Reset (Session) Password/Username Vulnerability
From: Vulnerability Lab <research () vulnerability-lab com>
Date: Sun, 18 Nov 2012 16:57:55 +0100
Skype Account Service - Reset (Session) Vulnerability
MSRC ID: 13050[bc]
Common Vulnerability Scoring System:
Skype is a proprietary voice-over-Internet Protocol service and software application originally created in 2003 by
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
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
Skype has 663 million registered users as of September 2011. The network is operated by Microsoft, which has its Skype
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)
The Vulnerability Laboratory Research Team discovered a critical session vulnerability in Microsofts Skype Account
2012-10-01: Researcher Notification & Coordination (VL - Benjamin Kunz Mejri)
2012-10-11: Vendor Notification (Skype Security)
2012-10-11: Vendor Notification (MSRC)
2012-10-23: Vendor Response/Feedback (MSRC)
2012-11-12: Vendor Fix/Patch *Hotfix (Skype)
2012-11-16: Public Disclosure (Vulnerability Laboratory)
Product: Skype Application & Software Account Service 2012 Q3
A critical Password Reset (session) vulnerability is detected in Microsofts Skype WebServer Auth System Application.
The vulnerability allows remote attackers without privileged application account to exchange and reset any skype
The critical application vulnerability is located in the recovery account function of the skype account service
In the recovery function is an auth request bound to the account session using the json form with jquery and the value
of the intercape.
The request itself is not sanitized. The value only check if exist and if empty but not validate the context again. The
bypass the token protection via live session tamper to reset any account by exchanging the values local to his own.
requires `processing to request` via jquery implement JSon form request. Since yet it is only manually possible to
exploit the remote
vulnerability by using a session tamper tools like tamper data. A remote attacker can, for example bypass the token
values like “*/+[New Account Details] or [New Account Details]+/*“ to reset random skype application accounts or
choosen account by changing usernames or passwords.
Successful exploitation of the critical remote vulnerability result in skype account compromise, skype account
mail information disclosure or lead to skype user account manipulation.
[+] Microsoft - Skype Service - https://login.skype.com/
[+] Account Application Service - https://login.skype.com/account
[+] Recovery Function - https://login.skype.com/account/password-automation
[+] JSon & jquery
Proof of Concept:
The vulnerability can be exploited by remote attacker without required user inter action.
For demonstration or reproduce ...
Required for Exploitation:
[+] Tamper Data or other live tamper software
[+] Web Browser like mozilla firefox, ie9 or chrome
[+] A random registered skype user account to get a not expired session
[+] Bypass the Skype Recovery Page (request tamper) to New Pass or Reset
[+] Bypass token protection via not empty value with positiv value(s) to match
[+] Hold the request via tamper include own values to setup the new password
[+] Decode captcha & send automatique value(s) -> Account Service (Remote Exploit)
2012-11-12: Vendor Fix/Patch (Skype)
The security risk of the remote password and username reset (session) vulnerability is estimated as critical.
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (bkm () vulnerability-lab com)
Vulnerability Laboratory [Research Team] - Chokri Ben Achour (meister () vulnerability-lab com)
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- Skype Account Service - Reset (Session) Password/Username Vulnerability Vulnerability Lab (Nov 19)