Date: Wed, 07 Feb 2007 14:26:02 -0500
From: iDefense Labs <labs-no-reply@...fense.com>
To: vulnwatch@...nwatch.org,  full-disclosure@...ts.grok.org.uk, 
	bugtraq@...urityfocus.com
Subject: iDefense Security Advisory 02.07.07: RARLabs
 Unrar Password Prompt Buffer Overflow Vulnerability

RARLabs Unrar Password Prompt Buffer Overflow Vulnerability

iDefense Security Advisory 02.07.07
http://labs.idefense.com/intelligence/vulnerabilities/
Feb 07, 2007

I. BACKGROUND

Unrar is a command line archive extractor for Windows and Linux. For more
information visit the vendor's site at the URL shown below.

http://www.rarlabs.com/

II. DESCRIPTION

Remote exploitation of a stack based buffer overflow vulnerability in
RARLabs Unrar may allow an attacker to execute arbitrary code with the
privileges of the user opening the archive.

Unrar is prone to a stack based buffer overflow when processing specially
crafted password protected archives.

III. ANALYSIS

Exploitation of the vulnerability could allow an attacker to execute
arbitrary code with the privileges of the user opening the file.
Exploitation would require that an attacker hosts a maliciously crafted
document on a website and entice users to visit the site. An attacker
could also e-mail the malicious document and use social engineering
techniques to trick the e-mail recipient into opening the document.

There are several mitigating factors for this vulnerability. Nearly all
Windows users will use the GUI based WinRAR to open archives, and it is
not vulnerable. If users are using the vulnerable command line based
unrar, they still need to interact with the program in order to trigger
the vulnerability. They must respond to the prompt asking for the
password, after which the vulnerability will be triggered. They do not
need to enter a correct password, but they must at least push the enter
key.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in version 3.60
for Linux and 3.61 for Windows. Previous versions may also be affected.

V. WORKAROUND

iDefense is currently unaware of any workarounds for this issue.

VI. VENDOR RESPONSE

RARLabs has addressed this vulnerability with the version 3.70 beta release
of WinRAR.

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

12/12/2006  Initial vendor notification
01/09/2007  Initial vendor response
02/07/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2006 iDefense, Inc.

Permission is granted for the redistribution of this alert electronically.
It may not be edited in any way without the express written consent of
iDefense. If you wish to reprint the whole or any part of this alert in
any other medium other than electronically, please e-mail
customerservice@...fense.com for permission.

Disclaimer: The information in the advisory is believed to be accurate at
the time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on, this
information.

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