bugtraq - Re: Regular Expression Denial of Service

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Date: Sat, 12 Sep 2009 00:10:08 +0300
From: Gadi Evron <ge@...uxbox.org>
To: Thierry Zoller <Thierry@...ler.lu>
Cc: Alex Roichman <Alexr@...ckmarx.com>, bugtraq@...urityfocus.com,
	Ilja van Sprundel <ilja@...esec.org>
Subject: Re: Regular Expression Denial of Service

Thierry Zoller wrote:
> Hi ,
> 
> With all due respect - this is known to be a vulnerability class since
> over  a  century.  Just  because  it  doesn't  have a acronym à la XSS
> doesn't mean it's not known to be a vulnerability. Can we please stop
> the  attitude of inventing acronyms for vulnerabilites, making it look
> like it's something new and funky.
> 
> It's  the  impact  of  something  that makes it a vulnerability no the
> name.

Thierry, you are quite right. However, I don't think they claimed it was 
a new class of vulnerabilities, and the responses since just added data 
to it. So I think that while you are factually correct, you misread 
their post. They shared their research with us.

	Gadi.


> 
> 
> GE> Alex Roichman wrote:
>>> Checkmarx Research Lab presents a new attack vector on Web applications. By
>>> exploiting the Regular Expression Denial of Service (ReDoS) vulnerability an
>>> attacker can make a Web application unavailable to its intended users. ReDoS
>>> is commonly known as a “bug” in systems, but Alex Roichman and Adar Weidman
>>> from Checkmarx show how serious it is and how using this technique, various
>>> applications can be “ReDoSed”. These include, among others, Server-side of
>>> Web applications and Client-side Browsers. The art of attacking the Web by
>>> ReDoS is by finding inputs which cannot be matched by Regexes and on these
>>> Regexes a Regex-based Web systems get stuck.
>>>
>>> For further reading:
>>> http://www.checkmarx.com/NewsDetails.aspx?id=23&cat=3
> 
> GE> Alex, nice work. Thank you for sharing it with us.
> 
> GE> I'd recommend taking a look at Ilja van Sprundel's work with regular 
> GE> expression bugs in his Unusual bugs presentation.
> GE> ... Where he played a bit with Google Code Search back in 2007, I think.
> GE> He helped Google out by giving them his research, of course.
> 
> GE> I found two versions online:
> GE> http://www.ruxcon.org.au/files/2006/unusual_bugs.pdf
> GE> http://www.slideshare.net/amiable_indian/unusual-bugs
> 
> GE> Ilja and I later discussed creating a real regex fuzzer to discover 
> GE> vulnerabilities, but I at least never had the time to play with it. He
> GE> might have, I am CC:ing him.
> 
> GE> My best to Adar,
> 
> GE> Gadi Evron,
> GE> http://www.gadievron.com/
>