Re: Report OWASP WAF Naxsi bypass Vulnerability

From: Jeffrey Walton <>
Subject: Re: Report OWASP WAF Naxsi bypass Vulnerability

Tracked through issue 65
(, fixed at
check-in R545 (

On Mon, Mar 25, 2013 at 10:00 PM,  <> wrote:
> OWASP WAF Naxsi bypass Vulnerability
> Certain unspecified input is not properly handed in
> naxsi_src/naxsi_utils.c naxsi_unescape_uri(u_char **dst, u_char **src,
> size_t size, ngx_uint_t type) before being used to filtered. This can
> be exploited to bypass some WAF rules.
> Naxsi site
> Affected
> All the version
> My site
> My nick name is Safe3
> It happens like that,the naxsi_unescape_uri function process the % url
> decode,if the next char after the % is a hex char and not after the
> hex char,then it will drop the % and the next char.So if we input a
> sql keyword "s%elect",it will come to "slect" instead,this is not the
> standard url decode way.Such as the IIS asp,it will process the
> "s%elect" as a result of "select",so we can bypass some
> WAF rules just like that.
> I afford a standard url decode function patch as the follow to fix this issue:
> ...

Copyright © 1995-2020 All rights reserved.