Vulnerability Note VU#935737

Adobe Flash Player may load arbitrary, malformed cross-domain policy files

Overview

Adobe Flash Player may load arbitrary, malformed cross-domain policy files. This could allow an attacker to control cross-domain data loading, potentially allowing the attacker to gain access to sensitive information or to manipulate content in other domains.

I. Description

Adobe Flash Player is a widely deployed application for multimedia viewing on the internet. A vulnerability exists in the way that Flash Player handles cross-domain policy files. An attacker could use a specially crafted cross-domain policy file to circumvent a site's Flash content data loading security polices.

From Security changes in Flash Player 9:

There is a possibility that a file on a server that does not appear to be a policy file may in fact be used as a policy file. For example, if a server permits uploads by users, but does not intend to open data for cross-domain access, it is possible that a user could deliberately construct a policy file but disguise it as a different type of file, such as an ordinary text, XML, or HTML file, or even as a binary type, such as a PNG or JPEG image file. A user who successfully uploaded this disguised policy file could then write a SWF file that takes advantage of the disguised policy file to load data from outside the server's domain.

II. Impact

A remote, unauthenticated attacker may be able to conduct cross-domain and cross-site scripting attacks on sites hosting Flash content. This could allow the attacker to read data or modify Flash content, possibly gaining access to sensitive information or spoofing web site content.

III. Solution

Adobe has released an update for Flash Player to address this vulnerability. Please see Adobe Security bulletin APSB07-20.

Limit access to Flash files

Limiting access to untrusted Flash files can prevent cross-site scripting attacks that use Flash files. Disable ActiveX controls in the Internet Zone in Microsoft Internet Explorer. See Securing Your Web Browser for more information. Consider using the NoScript extension to whitelist web sites that can run Flash in Mozilla browsers such as Firefox. See the NoScript FAQ for more information.

Systems Affected

Vendor	Status	Date Updated
Adobe	Vulnerable	24-Mar-2008

References

http://www.adobe.com/support/security/bulletins/apsb07-20.html
http://www.adobe.com/devnet/flash/articles/fplayer_security.html
http://www.adobe.com/devnet/flashplayer/articles/fplayer9_security.html
http://www.adobe.com/devnet/flashplayer/articles/cross_domain_policy.html
http://jvn.jp/jp/JVN%2345675516/index.html
http://secunia.com/advisories/28161/

Credit

Adobe credits Toshiharu Sugiyama of UBsecure, Inc. and JPCERT/CC for reporting this vulnerability.

This document was written by Dean Reges and Art Manion.

Other Information

Date Public	12/19/2007
Date First Published	03/25/2008 08:14:06 AM
Date Last Updated	03/25/2008
CERT Advisory
CVE Name	CVE-2007-6243
US-CERT Technical Alerts	TA07-355A
Metric	23.29
Document Revision	101

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Produced 2008 by US-CERT, a government organization
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