WebApp Sec: Re: Security Paper: Session Fixation Vulnerability in Web-based Applications

[Bill Pennington <billp () boarder org>]

Not to be an "I told you so" or anything since I didn't really tell 
anyone except the guys at SPI Dynamics but I noticed that problem (the 
reuse of session IDs between non-ssl and SSL sessions) about 3 years 
ago. It particularly was evident in BroadVision based applications. 
BroadVision released a paper to there clients I believe.
It really only became a big problem if the app echoed information back 
to the client. You could get CC info from active sessions pretty easily 
on some very large BroadVision based sites. If it didn't echo info you 
where kinda limited in your attack. On most apps i tested you could 
just add or remove stuff to peoples carts, while funny I did not think 
it was that big of an issue.


On Thursday, December 19, 2002, at 11:45 AM, Sverre H. Huseby wrote:

> |   ACROS Security is pleased to announce the publication of a
> |   security paper about a new class of attacks on web-based
> |   applications that we named "session fixation" attacks.
>
> Very interesting.  Particularly the part where one can include the
> session ID in a URL, as it doesn't depend on other bugs (such as XSS)
> in the target web site.  The paper is also very well written.
>
> The whole thing reminds me of something a friend pointed me to a
> couple of weeks ago: Using the same session id on both unencrypted and
> encrypted communication.  Many web sites let you start with plain
> HTTP, and switch to HTTPS as soon as you want to log in.  If someone
> sniffs the victim's session ID before the victim logs in over HTTPS,
> that someone may, in many cases, use that very same session ID to
> impersonate the victim after he has been authenticated.  The solution
> is, as with session fixation, to invalidate the session (and create a
> new one) when switching from unauthenticated to authenticated user.
>
> Well, merry Christmas and so on to everybody!
>
>
> Sverre.
>
> --
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