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Re: CVE request: is_a() function may allow arbitrary code execution in PHP 5.3.7/5.3.8
From: Stas Malyshev <smalyshev () sugarcrm com>
Date: Sun, 25 Sep 2011 01:56:59 -0700

Hi!

On 9/25/11 1:28 AM, Pierre Joye wrote:
It breaks the checks which leads to autoloader to accept bad input.
Yes, the autoloader should have sanity check in place but this BC
break changes the behavior and introduced this issue as well on top of
it.

I'm not sure either if we need a CVE as it is not a flaw in php itself
per se. However the BC break introduces flaws in working codes, and
that's a gray zone now.

Yes, it is a behavior change, and it shouldn't have happened in 5.3, the fact that it happened was a bad mistake, it is clear now. However, the security flaw is squarely in the code that a) misuses is_a b) doesn't have security checks and c) does not follow recommended best practices about PHP settings. As such, telling people that it was a flaw in PHP and that BC break reversal "fixed" it only gives them wrong ideas that their code was just fine. But in fact their code was broken and only by luck (and due to the haphazard way things were done in PHP where nobody bothered correlating function signatures with one another) in might have not been malfunctioning in this specific scenario. They need to fix that code ASAP, as they can not rely on luck anymore and they way is_a was changed is actually they way it should have worked from the start and the way is_subclass_of works right now.
--
Stanislav Malyshev, Software Architect
SugarCRM: http://www.sugarcrm.com/
(408)454-6900 ext. 227


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