============================================= Web Server Cache Poisoning in CMS Made Simple ============================================= CVE-2016-2784 Product Description =================== 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) ---------------- Proof of Concept ---------------- 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 ======== 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 ===== 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 ================= CMS Made Simple < 2.1.3 and < 1.12.2 Vulnerability Disclosure Timeline ================================= 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 ======= * Mickal Walter, I-Tracing (lab -at- i-tracing -dot- com) Website: http://www.i-tracing.com/