Pierluigi Paganini November 15, 2012

The news is circulating with insistence on the net, Skype is suffering from a vulnerability that can expose its users to serious risks, due this reason it has suspended the password reset process.

The Russian Blog Pixus.ru has published a post where it is described a workaround to hijack the accounts of the famous application. The vulnerability allows to an attacker to obtain full access to any Skype account simply knowing its email address used during the process of account creation.  The reality is that the vulnerability is not new, it was studied 3 months ago and disclosed only after the news as circulated on some famous social network platforms.

The attack allow to expose new and also chat conversations, messages, answerphone messages and user personal information. Currently Skype is investigating on the event and has suspended the password reset procedure that appears to be compromised.

A representative of company,  Leonas Sendrauskas.  company has released the following declaration:

“We have had reports of a new security vulnerability issue,” “As a precautionary step we have temporarily disabled password reset as we continue to investigate the issue further. We apologise for the inconvenience but user experience and safety is our first priority.”

Currently Skype have blocked the password reset page, the flaws is related to the possibility to signing up for a new Skype account using the email address of another registered user because it is not necessary to access to the victim’s email account to provide confirmation of the operations.

The creation of a new account is wrongly managed by Skype that doesn’t prevent it, but it limit its action to generate a warning that inform the user that the email address provided is already associated with another account. At this point the attacker simply ask for a password reset token and Skype will send it to his email, this allows the hacker to obtain the control of user’s original account.

The password change is requested by the attacker using the victims’s username from the bogus account created, the hijacker can access the resulting reset token using the Skype app itself with the second fake log-in locking out the account’s owner and access their details.

Fortunately Skype doesn’t show all the numbers of user’s registered credit card, attacker so can only exhaust user’s credit. A step by step guide has been published on on Russian forum Xeksec

Similar vulnerabilities are very dangerous and must be fixed as soon as possible, their exploit exposes to serious risks such as the possibility to hijack an accont for cyber espionage purpose. Don’t forget that in the past the possibility to spy on Skype communications has been debated for a long, different malware were developed to steal info e to intercept communication on client side. the popularity of Skype makes it a truly privileged target.
If the vulnerability was known for what reason it is discussed just now with all the fuss?

Pierluigi Paganini