AOL/AOL Instant Messenger Vulnerability

From: Robert Lyttle (robert@SUB-SEVEN.COM)
Date: 02/24/02 

Date:         Sun, 24 Feb 2002 02:36:09 -0800
From: Robert Lyttle <robert@SUB-SEVEN.COM>
To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM

AOL/AOL Instant Messenger Vulnerability

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Author: Robert Lyttle (robert@sub-seven.com)
Contributors: r0cky
Release Date: 02.24.02 - 2:00 AM

Disclaimer:
http://www.sub-seven.com and/or Robert Lyttle is not responsible for the misuse of the following information.

The below was executed against business associates with their express permission as proof of concept.

History:
This is the second significant public release of a hole within AOL's software, making it the 4th significant hole discovered in AOL software since Jan 1, 2002. (w00w00, this one, and two other private vulnerabilities) In 1999, 2000, and 2001 there were related vulnerabilities against AOL Instant Messenger.

Summary:
It is possible to retrieve the password of AOL Instant Messenger screen names through the http://free.aol.com, http://www.aol.com and http://www.aim.com websites. This then leading to possible gain of other accounts such as FTP, e-mail, and so on.

Susceptible to retrieving current password:
AOL Instant Messenger screen names that are registered to the same @aol.com address, but those that no longer exist in AOL's system (Usually 6 months after cancellation/termination of account.) Example: We have an AOL Instant Messenger screen name "hi mom" that is registered under the e-mail hi mom@aol.com - and since the hi mom@aol.com account is no longer in AOL's system, it is vulnerable.

Susceptible to take-over, but without current password:
AOL Instant Messenger screen names that are not currently in AOL's system. Social Engineering required.

How:
-Visit http://free.aol.com

-At the first page enter in any information you desire. (Remember this information if you plan on social engineering your way in later.) Now press continue.

-On the next page you will be asked for a screen name and password. Enter in an AOL Instant Messenger screen name and password that you own, that is NOT in AOL's system - Check the check box that says "Check here to use your AIM name on AOL" Now press continue.

-On the next page you will be asked for billing information and a new browser window will pop up. Click the "I Agree" button in the new browser window, it should close. Go back to the initial browser window and press the "Cancel" link on the bottom left hand corner.

-On the next page you will be brought to a new screen that talks about Joining AOL without a credit card. Now press continue.

The next 2 pages will be for verification -- Keep pressing "Continue" on the next 2 pages until you get to the page that asks for another screen name and password.

If you've done this correctly you will be greeted with "Sorry, <thename> is taken" then asked to enter another screen name and password as stated before. This is where you enter the screen name that you would like to retrieve the password from. (If you enter a screen name that is on AOL already, you will get error saying that it is already taken.) Other errors might occur when trying certain screen names, simply press the back button and try again.

So, say we enter "S7S Robert" and for the password field you would enter any password (DONT FORGET IT, this will be used in the following steps) Press the continue button and if the name was vulnerable you will be taken to a new page and greeted with "Welcome to America Online! Congratulations S7S Robert!" Now we have access to login to the http://www.aol.com AOLAnywhere service with the account that was just created.

-Now to retrieve the current password of S7S Robert, we visit http://www.aim.com and use the Lost Password feature found under Help. Enter in the screen name of the password to be retrieved and press Submit.

-Visit http://www.aol.com to use AOLAnywhere and login to the account using the password you chose before. You should have an e-mail in there from AOL with the password to the screen name.

If you didn't receive an e-mail from the Lost Password feature, this means that the AOL Instant Messenger screen name was not registered under the @aol.com address.

From here an attacker could change the password to the AOL Instant Messenger screen name and also try the same password against the victims other accounts.(FTP, SSH, etc)

Testing:
To test this simply register an AOL Instant Messenger name at http://www.aim.com and when it asks for the e-mail address to use, make it the same as the screen name and append @aol.com. For instance, if I want to test with "S7S Robert" I would enter the email address S7S Robert@aol.com as well. Once you've done that, you can use the above directions and see that you do not need the password used in the screen name registration process to retrieve it.

Solution:
I've e-mailed AOL multiple times before this advisory and have yet to receive a reply, so hopefully they are working on it. In the mean time, just make sure your AOL Instant Messenger screen name's email address isn't registered to its old @aol.com address.

- Robert Lyttle
- http://www.sub-seven.com

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