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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/