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Message-ID: <CAEUsJcrqgxz7Ev0BK_CUPXsgR+WShMcsNB0XnK6xGmGYHza1fw@mail.gmail.com> Date: Sat, 14 Feb 2015 03:09:05 +0100 From: "A. W." <a.l.g.m.wetzels@...il.com> To: fulldisclosure@...lists.org Subject: [FD] HumHub .htaccess file upload vulnerability and remote code execution [+] HumHub .htaccess file upload vulnerability and remote code execution [+] Discovered by: Jos Wetzels [+] Vendor: HumHub [+] Product: HumHub [+] Versions affected: 0.10.0 and earlier. [+] Advisory URL: https://www.leakfree.nl/advisories/leakfree_2015_003.html HumHub [1] versions 0.10.0 and prior suffer from a file upload sanitation vulnerability which allows an attacker to upload arbitrary .htaccess files with varying consequences [2]. On default installations this allows an attacker to achieve remote code execution while on a minority of installations it allows an attacker to execute an XSS or CSRF attack. Direct access to the uploads/file/ directory is denied by HumHub through the usage of .htaccess but an attacker can upload a .htaccess file starting with: <Files ~ "^\.ht"> # Uncomment line below for Apache >= 2.4 # Require all granted Order allow,deny Allow from all </Files> To allow direct access to the uploaded .htaccess file (and override general .htaccess settings within the directory). Depending on the enabled apache modules an attacker can execute various types of attacks ranging from information disclosure (when mod_info and mod_status are enabled), eg.: SetHandler server-info to remote code execution, eg.: AddType application/x-httpd-php .htaccess # <?php phpinfo(); ?> HumHub comes with a .htaccess.dist [3] file in the HumHub root directory which, if enabled by the user, prevents direct access to dotfiles (such as .htaccess, .svn, .git, etc.) using mod_rewrite. Since mod_rewrite is unaffected by the override (and using the RewriteEngine Off directive does not affect the .htaccess file itself) this prevents the above scenario from being exploitable. Regardless, it is still possible for an attacker to execute an unrestricted XSS or CSRF attack by abusing the ErrorDocument directive, eg.: ErrorDocument 403 <htmlpayload> Since the included .htaccess.dist is not enabled by default, however, an attacker can exploit this vulnerability to its full extent on an out-of-the-box HumHub installation. [*] References: 1. http://humhub.org 2. https://github.com/wireghoul/htshells 3. https://github.com/humhub/humhub/blob/master/.htaccess.dist _______________________________________________ Sent through the Full Disclosure mailing list https://nmap.org/mailman/listinfo/fulldisclosure Web Archives & RSS: http://seclists.org/fulldisclosure/
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