Modsecurity suffers from a cross site scripting bypass vulnerability.
e94fc45eeeb7a90c685b095d36b2bf62
# Product: Mod_security
# Author: Rafay Baloch
# Company: RHAINFOSEC
# Website: http://services.rafayhackingarticles.net
# Reported: 8/8/2013
# Fixed: 25/8/2013
# Status: Fixed
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Introduction
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The Mod_Security firewall is one of the most known WAF around, It has
anonline smoke test where we can check if a vector bypassed the regular
expressions that are meant to block the attacks. Recently,
Modsecurity setup a challenge for researchers, the challenge was
divided into two parts.
1) Bypassing Modsecurity's Firewall
2) Bypassing MentalJS
Luckily, i managed to bypass both of them.
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Details
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The modsecurity's rules were very strict, therefore i had to use a browser
bug to crack modsecurity's challenge. The browser bug involved
using seprators just before an event handler. I tried with lots of
seprators, however only /x0b worked for me in this case.
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POC
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<a/onmouseover[\x0b]=location='\x6A\x61\x76\x61\x73\x63\x72\x69\x70\x74\x3A\x61\x6C\x65\x72\x74\x28\x30\x29\x3B'>rhainfosec
===
Fix
===
The ModSecurity has updated the rule set and it now the detects the vector
as an xss vector. Along with that i also provided modsecurity with the list
of seprators that may have allowed for an attacker to create a working
bypass in other browsers too.
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