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| e-Matters 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. |
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Credit:
The information has been provided by E-Matters.
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Vulnerable systems:
PHP v3.10-v3.18, v4.0.1-v4.1.1
PHP supports multipart/form-data POST requests (as described in RFC1867) known as POST fileuploads. Unfortunately, there are several flaws in the php_mime_split function that could be used by an attacker to execute arbitrary code. During e-Matters' research, they have 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, e-Matters mentions that most of these vulnerabilities are exploitable only on Linux or Solaris. However, 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 completely rewritten for the 4.2.0 branch.
Vendor response:
27 February 2002 An updated version of PHP and the patch for these vulnerabilities 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 web server. Anyway, you should better install the fixed or a properly patched version to be safe.
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