Tag Archives: Microsoft IIS Vulnerability

Microsoft Contradiction

First of all, Microsoft is one of the best companies which leads us to the better world. But, nothing is free of fault except God!

I’m writing this post as a response to the Microsoft security response in: “http://blogs.technet.com/msrc/archive/2009/12/29/results-of-investigation-into-holiday-iis-claim.aspx”.

They said that “We’ve completed our investigation into the claims that came up over the holiday of a possible vulnerability in IIS and found that there is no vulnerability in IIS.”. Therefore, I realized that this is not a Microsoft IIS hole. So, it should be a feature of IIS 6.0! In my opinion it’s a good feature for the attackers to bypass the web uploaders protection. Now my question is: why have they removed this feature from IIS version 7 and 7.5 then? And why are the others so concerned about this feature and some people added it to their exploits collection?

I think it’s not even a critical bug for IIS, but it is highly critical for most of the web applications.

Besides, Microsoft is so wrong about the default configurations since they said “customers who are using IIS 6.0 in the default don’t need to worry about this issue”.  I think they should look at the shared servers default configurations as well as the dedicated ones.

Finally, I think Microsoft should fix this feature as soon as possible to eliminate its risks! And, it is up to the web security researchers and the web penetration testers to decide about the impact of this vulnerability on the web applications.


You can also look at these links:

–          http://www.darknet.org.uk/2009/12/microsoft-iis-semicolon-bug-leaves-servers-vulnerable/

–          http://www.esecurityplanet.com/trends/article.php/3855936/article.htm

–          http://www.securityfocus.com/bid/37460/references

Microsoft IIS Semi-Colon Vulnerability

I found a vulnerability in Microsoft IIS when I was searching about a method to execute an ASP file when we can only upload a JPG file.

The result was too simple, but interesting! I need only a semicolon between the “.asp” and the “.jpg” to execute an ASP file. So, the answer was “myfilename.asp;,jpg”. I have written some information about this vulnerability in:


I’ll try to update this PDF file if there was a need to add or change some information.

Description of this vulnerability from Secunia.com is:

Soroush Dalili has discovered a vulnerability in Microsoft Internet Information Services (IIS), which can be exploited by malicious people to potentially bypass certain security restrictions and compromise a vulnerable system.

The vulnerability is caused due to the web server incorrectly executing e.g. ASP code included in a file having multiple extensions separated by “;”, only one internal extension being equal to “.asp” (e.g. “file.asp;.jpg”). This can be exploited to potentially upload and execute arbitrary ASP code via a third-party application using file extensions to restrict uploaded file types.

The vulnerability is confirmed on a fully patched Windows Server 2003 R2 SP2 running Microsoft IIS version 6. Other versions may also be affected.

There are also several websites which wrote about this weakness:

1. Secunia Advisory: Microsoft IIS ASP Multiple Extensions Security Bypass

2. Securityfocus: Microsoft IIS Malformed Local Filename Security Bypass Vulnerability

3. The Register: Microsoft IIS vuln leaves users open to remote attack

4. VUPEN Security: Microsoft IIS File Extension Processing Security Bypass Vulnerability

5. Securitytracker: Microsoft Internet Information Services (IIS) Filename Extension Parsing Flaw May Let Users Bypass Security Controls