#2009-007 FCKeditor input sanitization errors

Description:

FCKeditor, a web based open source HTML text editor, suffers from a remote
file upload vulnerability.

The input of several connector modules is not properly verified before being
used, this leads to exposure of the contents of arbitrary directories on the
server filesystem and allows file uploading to arbitrary locations. The
affected code is remotely exposed before authentication. An attacker can
exploit this vulnerability to install remote shells on the victim server
among other things, it should be noted that this vulnerability is being
actively exploited in the wild.

Additionally several XSS vulnerabilities are present in the packaged samples
directory.

A patch and a new FCKeditor version will be made available on Monday July 6th
16:00 CET, this advisory will be updated with detailed information about the
issue and a security patch.

In the meantime we strongly recommend to implement the following
mitigation instructions:

  * removed unused connectors from 'editor\filemanager\connectors'

  * disable the file browser in config.ext

  * inspect all fckeditor folders on the server for suspicious files that
    may have been previously uploaded, as an example image directories
    (eg. 'fckeditor/editor/images/...') are well known target locations
    for remote php shells with extensions that match image files

  * completely remove the '_samples' directory

Affected version:

FCKeditor <= 2.6.4

(version 3.0 is unaffected as it does not have any built-in file browser)

Fixed version:

FCKeditor >= 2.6.4.1 (to be released on 2009-07-06 16:00 CET)

Credit: vulnerability report received from Vinny Guido <bigvin [at]
        hushmail [dot] com>.

CVE: CVE-2009-2265

Timeline:

2009-05-03: vulnerability reported received
2009-05-04: contacted fckeditor maintainer
2009-05-25: maintainer denies reported issues against latest version
2009-05-25: reporter confirms that latest version is affected
2009-06-21: maintainer forwards report to project security maintainer
2009-06-23: security maintainer confirms CurrentFolder vulnerability
2009-06-24: security maintainer provides patch
2009-06-29: assigned CVE
2009-07-03: preliminary advisory release with mitigation instructions due to
            wide exposure of the issue

Permalink:
http://www.ocert.org/advisories/ocert-2009-007.html

-- 
Andrea Barisani |                Founder & Project Coordinator
          oCERT | Open Source Computer Emergency Response Team

<lcars@ocert.org>                         http://www.ocert.org
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