If at first you don't succeed; call it version 1.0
Thursday, February 18, 2010

We all know what happens when a software vendor downplays the severity of a security vulnerability. It usually comes back to haunt them, when the vulnerability is eventually discovered by the bad guys and used to exploit innocent computer users.

Microsoft, Apple and even Mozilla have all been guilty of this in the past. Lately (and sadly), Adobe has joined this train.

We all have heard about the recent zero-day vulnerabilities in several widely deployed Adobe products. Adobe’s response to some of them has been at times outrageous. As another example, I recommend reading this blog post by Mike Bailey, regarding Adobe’s response to his latest discovery of security problems with Adobe’s Flash Origin-Policy.

Recently, I found a design flaw on Adobe’s website, which allows the abuse of the Adobe Download Manager to force the automatic installation of Adobe products, as well as other software products (e.g. Google Toolbar).

Instead of admitting that this design flaw is indeed a problem which can be abused by malicious attackers, Adobe decided to downplay this issue. When ZDNet Zero Day blogger Ryan Naraine reported my discovery to Adobe, the company sent this response:

"A few important points:

  • The Adobe Download Manager is intended for one-time use. The Adobe Download Manager is designed to remove itself from the computer after use at the next restart. The user can also remove the Adobe Download Manager prior to this using Add/Remove Programs.
  • The Adobe Download Manager can only be used to download the latest version of software hosted on Adobe.com.
  • The Adobe Download Manager presents a very large user dialog box when downloading software…”

I think they missed the whole point here. While it is true that the Adobe Download Manager is removed upon computer restart, the user, who has just updated their Adobe product (usually without the requirement to restart the computer after the update), is still exposed to forced automatic installation until they restart their computer.

This specific design flaw does indeed force installation of the latest version of Adobe products. But, what if there is a zero-day flaw in an Adobe product, and you have decided to remove it from your system because of that zero-day?  This is not a far-fetched “what if”. An attacker can force you to automatically download and install the vulnerable Adobe product, and then exploit the zero-day vulnerability in that product.

This is the kind of scenario that’s common when skilled, motivated attackers are going after select targets.

And yes, you do get a big dialog box when you are forced to download the software. Like this will really matter to the attacker, when all he wants is to get his malicious software on your machine.

On the same day I published my last blog post, I found yet another issue — a remote code execution flaw in the Adobe Download Manager. Basically, what I found is that an attacker can force an automatic download and installation of ANY executable he desires. So, if you go to Adobe’s website to install a security update for Flash, you really expose yourself to a zero-day attack.

Until Adobe decides to fix this vulnerability, I’m going to withhold the technical details of how to exploit this vulnerability. But, I can say that Adobe’s claim in regards to Adobe Download Manager use of SSL in downloading the software is simply not true.

I can only hope that Adobe will not downplay this vulnerability as well.

[Cross-post on ZDNet's Zero-Day Blog]

 


Thursday, February 18, 2010 9:39:12 PM UTC | Comments [2] | Security#
Saturday, February 20, 2010 1:46:06 PM UTC
Put them back in the closet!

...also you can point out that the download manager will run files even if they are not signed, a fact that could have also prevented the remote execution if it was checked (or at least, prevent remote execution from people without a spare $1,000)...

Drop me an email sometime, i think we have something to discuss.
Sunday, February 21, 2010 2:39:37 PM UTC
Thank you for valuable, effective and practical security information. You are the pro over professionals.
Comments are closed.     
Send me an Email
Follow me on Twitter
RSS Feeds
  
Blogroll
Archive
Admin Login
Sign In
Disclaimer
The opinions expressed herein are my own personal opinions and do not represent my employer's view in anyway.