Skip to main content

XSRF vulnerability in yahoomail..just flaw or security issue?

Although the attack is not severe in nature but can create interruption in user's logged in session.

Yahoomail doesn't use any button to log the user out. It simply provides a link 'Sign-Out' for the logging out the current session.
If the link is encoded in any form (or say disguised in tinyurl) and mailed to any logged in user in yahoomail and if he clicks it,the user who is visiting that page would immediately be logged out.
From the webserver's perspective, there is no difference whatsoever between a real user initiated browser request and the above URL retrieval.

It doesn't carry necessary credentials(e.g. anti XSRF tokens,or any uniquely token generated for the logged in user) with itself to tell the server that it's an extrenal request.Rather it will be using logged in user's credentials to complete the request!

The time discovered it , the other functions of yahoomail was not vulnerable except this "Sign-Out" function.

I had informed them about the vulnerablity but perhaps they didn't consider it an security issue but they now implement no of tokens and identifiers in the 'SignOut' link.

http://in.ard.yahoo.com/SIG=14vivapam/M=590705.12581184.13249026.10993486/D=inmail/S=398320003:HEAD/Y=IN/EXP=1231772641/L=WoCUrMtoEi.FJw6qSWn9mAVS3OIdt0lrP8EADW3f/B=5DsNmspWBvI-/J=1231765441885620/A=4559832/R=5/SIG=143d596d8/*http://login.yahoo.com/config/login?logout=1&.src=ym&.intl=in&.direct=2&.done=http://in.yahoo.com&.last=http://in.mail.yahoo.com/

But still it is not working! I mean the recipient is logged out of his session when he clicks on above link. That should not happen.
I think they are not paying attention to the issue since it is not affecting security of user or website.
In this way Gmail also has the same vulnerability(and might be many others..).
I just pointed out that it's an act of XSRF attack but whether it is an security issue or not, depends on the vendor's perception and how critical is the link that is being exploited.
It's a vulnerability but not Security Issue..I think....
Your Say??

References: http://www.squarefree.com/securitytips/web-developers.html
http://www.codinghorror.com/blog/archives/001171.html

Comments

Chintan Dave said…
Nilesh, I reported similar issues to Google as well. Technically, yes its is a vulnerability, however it makes no significant difference.

Practically speaking, it makes no sense to patch them. The resources spent to patch them are not justified.
January 23, 2009 at 9:01 PM
Nilesh Kumar said…
Yes I agree with you..in a post written to Gmail by me as well..I didn't stick to security impact of the issue rather I discussed about the way it has been implemented. See, underlying fact is that it performs an undesired action using logged in user's authentication.
This is the issue.
And when the same fact is used to exploit other links that may harm a user financially or personally it is called XSRF.
So I said the implementation in itself is wrong.
Anyways, thanks for commenting! :)
February 4, 2009 at 11:45 AM
Post a Comment

Popular posts from this blog

Using an AirPcap device in Windows with Wireshark

Capturing wireless traffic in a Windows environment is unfortunately not as easy as a setting change. As with most Windows-based software, drivers in Windows are often not open source and do not allow for configuration change into monitor mode. With this in mind, we must use a specialized piece of hardware known as an AirPcap device. Once you have obtained an AirPcap device you will be required to install the software on the accompanying CD to your analysis computer. The configurable options include: • Interface - Select the device you are using for your capture here. Some advanced analysis scenarios may require you to use more than one AirPcap device to sniff simultaneously on multiple channels. • Blink LED - Clicking this button will make the LED lights on the AirPcap device blink. This is primarily used to identify the specific adapter you are using if you are using multiple AirPcap devices. • Channel - In this field, you select the channel you want AirPcap to listen on. Extension C...
5 comments
Read more

Some one watching where you visited!

Yes... Mozilla has been susceptible to browser-history stealing java script code. Today, Giorgio posted some cool information about the exploit. Mozilla is already working on this. This bug has been reported. Actually they have set up a web site to show the proof-of-concept. Visit www.statrpanic.com in FF,Safari or Netscape and it will tell you which websites have you been already ! But I am not sure it will work in IE or not because my IE is not responding to the website. Clearing history of visited website makes you safe to this attack. I mean this is one way..may be there are other ways to exploit this. But I have found this effective. Try it yourself in FF and then in IE and see the results.
Post a Comment
Read more

Hijacking SSL

SSL has been in centerstage of researches as well as attacks for quite long time. Last year in a conference in Germany researchers showed how to generate duplicate certificates exploiting MD5 hashing to break SSL. Later in Black Hat, Maxie showed how to exploit a field in SSL certificates to sign an own forged certificate to present it to the client. The main feature of this attack was that the client will never get any warning dialog box by the browser and subsequently the hacker doing an MITM can see the conversation between the client and server. The client will even get a PADLOCK sign to be assured that all things are going via encryption, but in reality it's not. Maxie released a tool SSLStrip to carry out these attacks. The tool has been used by many researchers around the world to carry out the attacks. They all used Unix machines as many open source utilities makes it easier to run the tool on it. My attempt was to run the tool on a Windows machine. It has been never easy t...
4 comments
Read more