Re: CVE Request + Advisory: PHP str_repeat() sign mismatch based memory corruption

[Stanislav Malyshev <smalyshev () gmail com>]

Hi!

> About code execution, I haven't had the chance to focus on actual
> exploitation yet (I surely will in the near future), but as you can see
> from the original report (https://bugs.php.net/bug.php?id=69403), I
> pointed out several cases in which working on a so-crafted zval would
> lead to invalid memory access (with user controlled values as well), so
> I am pretty confident it is achievable.

These examples all seem to require specific code (like
'md5(str_repeat("a", 4294967294-1));') to be run. The probability that
applications would contain this specific code with str_repeat argument
controlled by remote user seems to be pretty low. However, if you can
show exploiting this on a code of an application that is not specially
crafted to demonstrate this issue, or at least resembles code that is
likely to be deployed in a real application, I will gladly change my
opinion.

-- 
Stas Malyshev
smalyshev () gmail com