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      Core Security Technologies - CoreLabs Advisory
           http://www.coresecurity.com/corelabs/

Blender .blend Project Arbitrary Command Execution



1. *Advisory Information*

Title: Blender .blend Project Arbitrary Command Execution
Advisory Id: CORE-2009-0912
Advisory URL:
http://www.coresecurity.com/content/blender-scripting-injection
Date published: 2009-11-05
Date of last update: 2009-11-04
Vendors contacted: Blender Foundation
Release mode: User release



2. *Vulnerability Information*

Class: Failure to Sanitize Data into a Different Plane [CWE-74]
Impact: Code execution
Remotely Exploitable: Yes (client side)
Locally Exploitable: No
Bugtraq ID: 36838
CVE Name: CVE-2009-3850



3. *Vulnerability Description*

Blender [2] is a 3D graphics application released as free software. It
can be used for modeling, texturing, rendering, particle, and other
simulations and creating interactive 3D applications, including games.

Blender embeds a python interpreter to extend its functionality.
Blender .blend project files can be modified to execute arbitrary
commands without user intervention by design. An attacker can take
full control of the machine where Blender is installed by sending a
specially crafted .blend file and enticing the user to open it.


4. *Vulnerable packages*

   . Blender 2.49b
   . Blender 2.40
   . Blender 2.35a
   . Blender 2.34
   . Older versions are probably affected too, but they were not checked.


5. *Vendor Information, Solutions and Workarounds*

The vendor did not provide fixes or workaround information.

To determine if a .blend file is suspicious you could parse the
content of the file [3] searching for a SDNA [4] of type ScriptLink
[5] with python code bound to an "onLoad" action.


6. *Credits*

This vulnerability was discovered and researched by Diego Juarez and
Sebastian Tello from Core Security Technologies during Bugweek 2009 [1].

The publication of this advisory was coordinated by Fernando Russ from
Core Security Advisories Team.


7. *Technical Description / Proof of Concept Code*

Blender [2] .blend project files can be modified to execute arbitrary
commands without user intervention by design. An attacker can take
full control of the machine where Blender is installed sending a
specially crafted .blend file and enticing the user to open it.

These are the steps to reproduce the issue:

   . Open the "Text Editor" Panel.
   . Right click on the canvas and select "New".
   . Write your python code there. For instance:

/-----
      import os
      os.system("calc.exe")
- -----/

   . In the text name field (TX:Text.001) input a name for your
script, e.g.: TX:myscript.
   . Open the "Buttons Window" panel.
   . From the "panel" dropdown choose "Script".
   . Check that "enable script links" is active.
   . Click on "new".
   . Select the script you created (e.g. myscript).
   . Choose "OnLoad" from the event dropdown list.
   . In the "User Preferences" panel, select File->Save, and save your
project.


8. *Report Timeline*

. 2009-10-19:
Core Security Technologies notifies to the Blender foundation of the
vulnerabilty and announces its initial plan to publish this advisory
on October 30th, 2009.

. 2009-10-20:
The Blender foundation answers that "We are a free software project,
all issues are openly discussed. Just post the discoveries you made
for everyone to look at."

. 2009-10-27:
Core sends a draft advisory to the Blender Foundation for this flaw.
Core also reminds the vendor its intention to publish the content on
October 30th, 2009.

. 2009-10-27:
BID 36838 was assigned to this issue

. 2009-11-03:
CVE 2009-3850 was assigned to this issue

. 2009-11-03:
The Blender Foundation didn't acknowledge or answer our comunications
anymore.

. 2009-11-05:
The advisory CORE-2009-0912 is published.



9. *References*

[1] The author participated in Core Bugweek 2009 as member of the team
"Gimbal Lock N Load".
[2] http://www.blender.org/
[3] http://www.atmind.nl/blender/mystery_ot_blend.html
[4] http://www.atmind.nl/blender/blender-sdna.html
[5] http://www.atmind.nl/blender/blender-sdna.html#struct:ScriptLink


10. *About CoreLabs*

CoreLabs, the research center of Core Security Technologies, is
charged with anticipating the future needs and requirements for
information security technologies. We conduct our research in several
important areas of computer security including system vulnerabilities,
cyber attack planning and simulation, source code auditing, and
cryptography. Our results include problem formalization,
identification of vulnerabilities, novel solutions and prototypes for
new technologies. CoreLabs regularly publishes security advisories,
technical papers, project information and shared software tools for
public use at: http://www.coresecurity.com/corelabs.


11. *About Core Security Technologies*

Core Security Technologies develops strategic solutions that help
security-conscious organizations worldwide develop and maintain a
proactive process for securing their networks. The company's flagship
product, CORE IMPACT, is the most comprehensive product for performing
enterprise security assurance testing. CORE IMPACT evaluates network,
endpoint and end-user vulnerabilities and identifies what resources
are exposed. It enables organizations to determine if current security
investments are detecting and preventing attacks. Core Security
Technologies augments its leading technology solution with world-class
security consulting services, including penetration testing and
software security auditing. Based in Boston, MA and Buenos Aires,
Argentina, Core Security Technologies can be reached at 617-399-6980
or on the Web at http://www.coresecurity.com.


12. *Disclaimer*

The contents of this advisory are copyright (c) 2009 Core Security
Technologies and (c) 2009 CoreLabs, and may be distributed freely
provided that no fee is charged for this distribution and proper
credit is given.


13. *PGP/GPG Keys*

This advisory has been signed with the GPG key of Core Security
Technologies advisories team, which is available for download at
http://www.coresecurity.com/files/attachments/core_security_advisories.asc.


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