[Esapi-user] [Esapi-dev] ESAPI URL validation RX is vulnerable to DoS

Jim Manico jim.manico at owasp.org
Thu Oct 14 10:03:17 EDT 2010

This is a great finding. It's especially a problem when using ESAPI with a
cloud service that charges you by cpu usage.


I think RegEx based security, in general, is a very poor paradigm. More on
that later. We should use Java's URL classes to do this kind of validation.
The RegEx was a mistake, in my opinion. I'll push out a proof of concept to
"fix" this after our next release.


- Jim


From: esapi-dev-bounces at lists.owasp.org
[mailto:esapi-dev-bounces at lists.owasp.org] On Behalf Of Mostafa Siraj
Sent: Thursday, October 14, 2010 6:39 PM
To: Esapi-dev at lists.owasp.org; esapi-user at lists.owasp.org
Subject: [Esapi-dev] ESAPI URL validation RX is vulnerable to DoS



Microsoft release a regex fuzzer tool, the tool purpose is to identify weak
regular expressions that are vulnerable to Denial of Service (DoS)

I tested the tool against the default regular expressions in
validation.properties on ESAPI and found that 
Validator.URL is vulnerable to DoS


Attack Vector=

You can download Microsoft Regex Fuzzer from this link

You can test the vulnerable regular expression against the attack vector
using any Regex tool like Rad <http://www.radsoftware.com.au/regexdesigner/>

An article that shows how regular expression DoS can be used to harm SaS
investors is here


Best Regards,

Mostafa Siraj <http://twitter.com/mostafasiraj> 


Our deepest fear is not that we are inadequate. Our deepest fear is that we
are powerful beyond measure. It is our light, not our darkness, that most
frightens us. We ask ourselves, who am I to be brilliant, gorgeous,
talented, and fabulous?Actually, who are you not to be? You are a child of
God. Your playing small doesn't serve the world. There's nothing enlightened
about shrinking so that other people won't feel insecure around you. We are
all meant to shine, as children do. We are born to make manifest the glory
of God that is within us. It's not just in some of us, it's in everyone. And
as we let our own light shine, we unconsciously give other people permission
to do the same. As we are liberated from our own fear, our presence
automatically liberates others. - Nelson Mandela


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