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Re: CVE request: is_a() function may allow arbitrary code execution in PHP 5.3.7/5.3.8
From: Rasmus Lerdorf <rasmus () php net>
Date: Sun, 25 Sep 2011 18:38:40 +0200

On 09/25/2011 04:10 PM, Pierre Joye wrote:
On Sun, Sep 25, 2011 at 3:47 PM, Zeev Suraski <zeev () zend com> wrote:

There aren't any security issues in PHP in that context.  Assigning a CVE to PHP in that context would create the 
impression that there is indeed an issue in PHP here.
It's not a matter of who's 'guilty' in terms of positioning - but in terms of where the actual security issue 
resides.  And it does not reside in PHP.

So I agree with Stas, it doesn't make sense to have a CVE here.  Otherwise, almost every change we make, including 
bug fixes, could somehow result in some faulty piece of code somewhere becoming vulnerable to something.

The whole point is that some code was not having any issue before this
change. If the check was done earlier using is_a then this unexpected
behavior will happen, and that actually causes a security issue in
existing working code. The example in the blog post is very good one,
it clearly shows that the impact on existing code is not only about
wrongly implemented autoloader, or someone not disabling
allow_url_fopen (I can imagine local file include being an issue as
well under some circumstances).

All in all, there is no shame or bad image to get a new CVE for
something like that, I even see it as a good thing as it will:

I didn't read the thread from the beginning, but is there an actual
exploit here? Presumably the autoloader code in question isn't doing an
fopen/eval to execute the code and since allow_url_include is disabled
by default, remote includes aren't an issue in the default install. So
are we talking about the tiny number of people who have explicitly
enabled allow_url_include and are running the code with this bad autoloader?

-Rasmus


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