XML External Entity (XXE) Injection Vulnerability in Apache Batik (Java
SVG Toolkit)
====================================================================================
Researcher: Kevin Schaller <kschaller@ernw.de>


Description
===========
Batik is a Java-based toolkit for applications or applets that want to
use images in the
Scalable Vector Graphics (SVG) format for various purposes, such as
display, generation or
manipulation. [1]

Batik offers several classes for svg to png/jpg conversion, which suffer
from a XML External
Entity Injection due to the evaluation of external entities within the
given svg file. If an
application offers the possibility to upload a svg file an attacker can
put in a malicious formed
file and retrieve sensitive information such as the content of files of
the respective server.
The type of file that can be retrieved depends on the user context in
which the application is running.

Further information about the vulnerability can be seen here [2] and
here [3].


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Medium


CVSS Base Score
===============
6.4 (AV:N / AC:L / Au:N / C:P / I:N / A:P)


CVE-ID
======
CVE-2015-0250


Impact
======
Files lying on the filesystem of the server which uses batik can
be revealed to arbitrary users who send maliciously formed svg
files. The file types that can be shown depend on the user context
in which the exploitable application is running. If the user is 'root'
a full compromise of the server--including confidential or sensitive
files--would be possible.

XXE can also be used to attack the availability of the server
via denial of service as the references within a xml document
can trivially trigger an amplification attack.


Proof of Concept
================
A fully documented proof of concept can be downloaded here: [4]


Mitigation
==========
Upgrade to Batik 1.8+ 


Affected Versions
=================
All versions
1.0 - 1.7 (current)


Timeline
========
2015-01-22: Apache informed via email - no response
2015-02-08: Remainder sent via email
2015-02-10: Vulnerability confirmed and fix has been tested and
confirmed to work
2015-03-17: Release of a fixed version and public dislocure


Credits
=======
Timo Schmid <tschmid@ernw.de>


References
==========
[1] http://xmlgraphics.apache.org/batik/
[2]
http://www.insinuator.net/2015/03/xxe-injection-in-apache-batik-library-cve-2015-0250/
[3] https://www.owasp.org/index.php/XML_External_Entity_%28XXE%29_Processing
[4] https://www.ernw.de/download/xxe_batik.tar.xz


Disclaimer
==========
The information herein contained may change without notice. Use of this
information constitutes acceptance for use in an AS IS condition. There
are NO
warranties, implied or otherwise, with regard to this information or its
use.
Any use of this information is at the user's risk. In no event shall the
author/
distributor be held liable for any damages whatsoever arising out of or in
connection with the use or spread of this information.

-- 
Kevin Schaller

ERNW GmbH - Carl-Bosch-Str. 4 - 69115 Heidelberg - www.ernw.de
Tel. +49 6221 480390 (Zentrale) - Fax +49 6221 419008 - Cell +49 151 16227194

Handelsregister Mannheim: HRB 337135
Geschaeftsfuehrer: Enno Rey

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