[WEB SECURITY] [SC-L] Java DOS

James Manico jim at manico.net
Sat Feb 12 19:23:37 EST 2011


Hey Brian,

I think it's critical that we discuss these issues with prescriptive
remediation advice.

1) Update your JVM, often easier said then done
2) Build a blacklist filter looking for this specific numerical attack
range. I already patched this in the ESAPI for Java security library
which you will see in ESAPI 2.0 rc12 within a week or 2, but the
credit goes to Adobe for being on top of this (and to Williams for
pointing this out to me).

http://blogs.adobe.com/asset/2011/02/year-of-the-snail.html

I'm impressed team Adobe!

-Jim Manico
http://manico.net

On Feb 12, 2011, at 10:13 PM, Brian Chess <brian at fortify.com> wrote:

> There's a very interesting vulnerability in Java kicking around.  I wrote about it here:
>  http://blog.fortify.com/blog/2011/02/08/Double-Trouble
>
> In brief, you can send Java (and some versions of PHP) into an infinite loop if you can provide some malicious input that will be parsed as a double-precision floating point number.
>
> This code used to look like the beginnings of some decent input validation:
>   Double.parseDouble(request.getParameter("d"));
> Now it's the gateway to an easy DOS attack.  (At least until you get a patch from your Java vendor, many of whom haven't released patches yet.  Oracle has released a patch.  Do you have it?)
>
> Until a few days ago, all major releases of Tomcat made matters worse by treating part of the Accept-Language header as a double.  In other words, you don't need to have any double-precision values in *your* code for your app to be vulnerable.
>
> The SC-L corner of the world puts a lot of emphasis on training and on looking for known categories of vulnerabilities.  That's all goodness.  But this example highlights the fact that we have to build systems and procedures that can quickly adapt to address new risks.
>
> Brian
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