Advisory 01/2002
PHP remote vulnerabilities
Release Date: 2002/02/27 Author: Stefan Esser [s.esser@ematters.de] Application: PHP v3.10-v3.18, v4.0.1-v4.1.1 Severity: Several vulnerabilities in PHP's fileupload code allow remote compromise Risk: Critical Reference: http://security.e-matters.de/advisories/012002.html Last Modified:   2002/02/27
Overview We found several flaws in the way PHP handles multipart/form-data POST requests. Each of the flaws could allow an attacker to execute arbitrary code on the victim's system.
Details PHP supports multipart/form-data POST requests (as described in RFC1867) known as POST fileuploads. Unfourtunately there are several flaws in the php_mime_split function that could be used by an attacker to execute arbitrary code. During our research we found out that not only PHP4 but also older versions from the PHP3 tree are vulnerable. The following is a list of bugs we found: PHP 3.10-3.18 - broken boundary check (hard to exploit) - arbitrary heap overflow (easy exploitable) PHP 4.0.1-4.0.3pl1 - broken boundary check (hard to exploit) - heap off by one (easy exploitable) PHP 4.0.2-4.0.5 - 2 broken boundary checks (one very easy and one hard to exploit) PHP 4.0.6-4.0.7RC2 - broken boundary check (very easy to exploit) PHP 4.0.7RC3-4.1.1 - broken boundary check (hard to exploit) Finally I want to mention that most of these vulnerabilities are exploitable only on linux or solaris. But the heap off by one is only exploitable on x86 architecture and the arbitrary heap overflow in PHP3 is exploitable on most OS and architectures. (This includes *BSD) Users running PHP 4.2.0-dev from cvs are not vulnerable to any of the described bugs because the fileupload code was completly rewritten for the 4.2.0 branch.
Proof of Concept e-matters is not going to release exploits for any of the discovered vulnerabilities to the public.
Vendor Response Because I am part of the php developer team there is not much I can write here...   27 February 2002 An updated version of php and the patch for these vulnerabilites are now available at: http://www.php.net/downloads.php
Recommendation If you are running PHP 4.0.3 or above one way to workaround these bugs is to disable the fileupload support within your php.ini (file_uploads = Off) If you are running php as module keep in mind to restart the webserver. Anyway you should better install the fixed or a properly patched version to be safe.
Sidenotice This advisory is so short because I don't want to give out more info than is needed. Users running the developer version of php (4.2.0-dev) are not vulnerable to these bugs because the fileupload support was completly rewritten for that branch.