Advisory from iDefense Labs:

http://labs.idefense.com/intelligence/vulnerabilit...id=472

RARLabs Unrar Password Prompt Buffer Overflow Vulnerability

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.