STG Security Advisory: [SSA-20041215-17] Vulnerability of uploading files

with multiple extensions in JSBoard

Revision 1.0

Date Published: 2004-12-15 (KST)

Last Update: 2004-12-15

Disclosed by SSR Team (advisory (at) stgsecurity (dot) com [email concealed])

Summary

========

JSBoard is one of widely used web BBS applications in Korea. 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

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

JSBoard 2.0.8 and prior.

JSBoard 1.3.11 and prior.

Vendor Status: FIXED

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

2004-12-08 Vulnerability found.

2004-12-08 JSBoard developer notified.

2004-12-09 Update version released.

2004-12-15 Official release.

Details

=======

JSBoard doesn't implemented in "include/parse.php" to check multiple

extensions of uploaded files, e.g. attack.php.hwp, 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.hwp 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

=========

JSBoard 2.x branch : Update to 2.0.9

http://kldp.net/frs/download.php/1670/jsboard-2.0.9.tar.gz

JSBoard 1.x branch : Update to 1.3.13

http://kldp.net/frs/download.php/1668/jsboard-1.3.13.tar.gz

Vendor URL

==========

http://kldp.net/projects/jsboard/

Credits

======

Jeremy Bae at STG Security

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