Pi3Web <= 2.0.13 (ISAPI) Remote Denial of Service Exploit

2008-11-13 20:30:02

Pi3Web ISAPI DoS vulnerability

Discovered by: Hamid Ebadi
CSIRT Team Member
Amirkabir University CSIRT Laboratory (APA Laboratory)

[email protected]


Introduction
Pi3Web is a free, multithreaded, highly configurable and extensible HTTP server and development environment for cross platform internet server development and deployment. Pi3web is vulnerable to a denial of service (DoS) vulnerability whenever an invalid ISAPI module is requested from server.

Vulnerable version
Pi3Web <=2.0.13

Vulnerability
By requesting the following URL from pi3web the server crashes:
http://WEB_SITE/isapi/users.txt

EnhPi3.exe -Bad Image
The application or DLL c:\Pi3Web\Isapi\users.txt is not a valid Windows image. Please check this against your installation diskette The vulnerability is caused.

The crash is due to insufficient checks for incoming requests. Whenever a file in ISAPI directory, which is not a valid DLL is requested, the server tries to load it into memory as a DLL library and a crash happens.

Workaround
Before an official patch is released, use one of the following workarounds to mitigate the problem:

1. Disable ISAPI mapping in server configuration in Server Admin > Mapping Tab.
2. Delete the users.txt, install.daf and readme.daf in ISAPI folder.


Credit
This vulnerability has been discovered by Hamid Ebadi from Amirkabir university CSIRT laboratory.

[email protected]
https://www.ircert.cc

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Fixes

No fixes

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