VLC Activex Bad Pointer Initialization Vulnerability
Core Security Technologies - CoreLabs Advisory
Title: VLC Activex Bad Pointer Initialization Vulnerability
Advisory ID: CORE-2007-1004
Advisory URL: http://www.coresecurity.com/?action=item&id=2035
Date published: 2007-12-03
Date of last update: 2007-12-03
Vendors contacted: VLC
Release mode: Coordinated Release
VLC player is a popular multimedia player for various audio and video formats, and various streaming protocols.
A vulnerability has been found in the ActiveX control DLL (axvlc.dll) used by VLC player. This library contains three methods whose parameters are not correctly checked, and may produce a bad initialized pointer. By providing these functions specially crafted parameters, an attacker can overwrite memory zones and execute arbitrary code.
VLC media player version 0.86, 0.86a, 0.86b y 0.86c.
VLC media player versions prior to 0.86.
VLC media player version 0.86d.
Vendor Information, Solutions and Workarounds
VLC media player 0.8.6d adresses this issue and introduces further usability fixes.
Download it from the VideoLAN project website: http://www.videolan.org/
This vulnerability was discovered by Ricardo Narvaja (Ricnar) from the Exploit Writers team of Core Security Technologies.
Technical Description / Proof of Concept Code
The ActiveX control DLL (axvlc.dll) contains three methods whose parameters are not correctly checked, and may produce a bad initialized pointer. By providing these functions specially crafted parameters, an attacker can overwrite memory zones and execute arbitrary code.
The vulnerable functions are:
Sub addTarget ( ByVal uri As String , ByVal options As Variant , ByVal mode As VLCPlaylistMode , ByVal Position As Long) Function getVariable (ByVal name As String) Sub setVariable ( ByVal name As String , ByVal value As Variant)
The following assembly code is where the axvlc.dll library crashes. The pointer that is read to be executed, can be overwritten, depending on how the strings are sent. It also requires that previously other files are loaded that left the pointer bad initialized, with the value that the attacker needs to jump to his own code.
000113CD FF50 14 CALL DWORD PTR DS:[EAX+14] 000113D0 8B53 08 MOV EDX,DWORD PTR DS:[EBX+8] 000113D3 85D2 TEST EDX,EDX
The following is a PoC HTML file, using one of the vulnerable methods (addTarget).
- 2007-10-26: Core notifies the VLC team of the vulnerability.
- 2007-10-29: Technical details sent by Core to VLC.
- 2007-11-23: VLC notifies Core that a fix has been produced, and will be released in VLC version 0.8.6d.
- 2007-11-30: VLC releases version 0.8.6d, which fixes this vulnerability.
- 2007-12-03: CORE-2007-1004 advisory is published.
 Practical demonstration of VLC ActiveX vulnerability
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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. 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 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.
The contents of this advisory are copyright (c) 2007 CORE Security Technologies and (c) 2007 CoreLabs, and may be distributed freely provided that no fee is charged for this distribution and proper credit is given.
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