STG Security Advisory: [SSA-20041215-18] Vulnerability of uploading files

with multiple extensions in phpBB Attachment Mod



Revision 1.1

Date Published: 2004-12-15 (KST)

Last Update: 2004-12-15

Disclosed by SSR Team (advisory@stgsecurity.com) 



Summary

========

phpBB Attachment Mod is file upload module for phpBB. However, an input

validation flaw can cause malicious attackers to run arbitrary commands with

the privilege of the HTTPD process, which is typically run as the nobody

user.



Vulnerability Class

===================

Implementation Error: Input validation flaw



Impact

======

High : arbitrary command execution.



Affected Products

================

Attachment Mod 2.3.10 and prior.



Vendor Status: FIXED

====================

2004-12-08 Vulnerability found.

2004-12-08 Attachment Mod developer notified.

2004-12-13 Update version released.

2004-12-15 Official release.



Details

=======

Attachment Mod doesn't implemented to check multiple extensions of uploaded

files, e.g. attack.php.rar, so malicious attackers can upload arbitrary

script files (php, pl, cgi, etc) to a web server. This is originated from a

feature of Apache MIME module (mod_mime), which regards attack.php.rar as a

normal PHP file and execute the file through mod_php module with the

privilege of the HTTPD process.

cf. http://httpd.apache.org/docs/mod/mod_mime.html - "Files with Multiple

Extensions" : it's a feature, not a bug.



Solution

=========

Update to 2.3.11

http://www.opentools.de/board/viewtopic.php?t=3590 



Vendor URL

==========

http://www.opentools.de/ 



Credits

======

Jeremy Bae at STG Security