Vulnerability Note VU#486225

Adobe Flash ActionScript AVM2 newfunction vulnerability

Overview

Adobe Flash contains a vulnerability in the handling of the ActionScript newfunction instruction, which can allow a remote, unauthenticated attacker to execute arbitrary code.

I. Description

Adobe Flash 9 and later versions support ActionScript 3, which is executed by the ActionScript Virtual Machine 2 (AVM2). The AVM2 takes ActionScript Bytecode (ABC) as input, and it is just-in-time (JIT) compiled into processor-specific instructions. Certain malformed use of the AVM2 newfunction instruction can result in an exploitable crash. This vulnerability affects Flash Player 9 through 10.0.45.2. Adobe Reader 9, Acrobat 9, and other Adobe products (including Photoshop CS3, PhotoShop Lightroom, Freehand MX, Fireworks) provide Flash support independent of Flash Player.

This vulnerability is being exploited in the wild. Exploit code for this vulnerability is publicly available.

II. Impact

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), PDF file, Microsoft Office document, or any other document that supports embedded SWF content, an attacker may be able to execute arbitrary code.

III. Solution

Apply an update

This vulnerability is addressed in Flash 10.1. Please see Adobe Security Bulletin APSB10-14 for more details.

Disable Flash in your web browser

Disable Flash or selectively enable Flash content as described in Securing Your Web Browser.

Disable Flash and 3D & Multimedia support in Adobe Reader 9

Flash and 3D & Multmedia support are implemented as plug-in libraries in Adobe Reader. Disabling Flash in Adobe Reader will only mitigate attacks using an SWF embedded in a PDF file. Disabling 3D & Multimedia support does not directly address the vulnerability, but it does provide additional mitigation and results in a more user-friendly error message instead of a crash.

To disable Flash and 3D & Multimedia support in Adobe Reader 9 on Microsoft Windows, delete or rename these files:

"%ProgramFiles%AdobeReader 9.0Readerauthplay.dll"
"%ProgramFiles%AdobeReader 9.0Reader t3d.dll"

For Apple Mac OS X, delete or rename these files:

"/Applications/Adobe Reader 9/Adobe Reader.app/Contents/Frameworks/AuthPlayLib.bundle"
"/Applications/Adobe Reader 9/Adobe Reader.app/Contents/Frameworks/Adobe3D.framework"

For GNU/Linux, delete or rename these files (locations may vary among distributions):

"/opt/Adobe/Reader9/Reader/intellinux/lib/libauthplay.so"
"/opt/Adobe/Reader9/Reader/intellinux/lib/librt3d.so"

File locations may be different for Adobe Acrobat or other Adobe products that include Flash and 3D & Multimedia support. Disabling these plug-ins will reduce functionality and will not protect against SWF files hosted on websites. Depending on the update schedule for products other than Flash Player, consider leaving Flash and 3D & Multimedia support disabled unless they are absolutely required.

Remove Flash

Adobe has provided a TechNote with utilities for uninstalling the Flash Player plug-in and ActiveX control on Windows and Mac OS X systems. Removing these components can mitigate the web browser attack vector for this vulnerability. Note that this will not remove the instances of Flash Player that is installed with Adobe Reader 9 or other Adobe products.

Enable DEP in Microsoft Windows

Consider enabling Data Execution Prevention (DEP) in supported versions of Windows. DEP should not be treated as a complete workaround, but it can mitigate the execution of attacker-supplied code in some cases. Microsoft has published detailed technical information about DEP in Security Research & Defense blog posts "Understanding DEP as a mitigation technology" part 1 and part 2. Use of DEP should be considered in conjunction with the application of patches or other mitigations described in this document.

Disable JavaScript in Adobe Reader and Acrobat

Disabling JavaScript can help mitigate against some techniques that use Adobe Reader as an attack vector.

To disable JavaScript in Adobe Reader:

1. Open Adobe Acrobat Reader.
2. Open the Edit menu.
3. Choose the Preferences... option.
4. Choose the JavaScript section.
5. Uncheck the Enable Acrobat JavaScript checkbox.

Disabling JavaScript will not resolve the vulnerabilities, it will only disable the vulnerable JavaScript component. When JavaScript is disabled, Adobe Reader and Acrobat prompt to re-enable JavaScript when opening a PDF that contains JavaScript.

Prevent Internet Explorer from automatically opening PDF documents

The installer for Adobe Reader and Acrobat configures Internet Explorer to automatically open PDF files without any user interaction. This behavior can be reverted to the safer option of prompting the user by importing the following as a .REG file:

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOTAcroExch.Document.7]
"EditFlags"=hex:00,00,00,00

Disable the displaying of PDF documents in the web browser

Preventing PDF documents from opening inside a web browser reduces the attack surface. If this workaround is applied to updated versions of Adobe Reader and Acrobat, it may protect against future vulnerabilities.

To prevent PDF documents from automatically being opened in a web browser with Adobe Reader:

1. Open Adobe Acrobat Reader.
2. Open the Edit menu.
3. Choose the Preferences... option.
4. Choose the Internet section.
5. Uncheck the Display PDF in browser checkbox.

Vendor Information

Vendor	Status	Date Notified	Date Updated
Adobe	Affected	2010-01-25	2010-06-10

References

http://www.cert.org/tech_tips/securing_browser/
http://www.adobe.com/support/security/bulletins/apsb10-14.html
http://www.adobe.com/support/security/advisories/apsa10-01.html
http://www.adobe.com/devnet/actionscript/articles/avm2overview.pdf
http://labs.adobe.com/technologies/flashplayer10/
http://blog.zynamics.com/2010/06/09/analyzing-the-currently-exploited-0-day-for-adobe-reader-and-adobe-flash/
http://www.symantec.com/connect/blogs/analysis-zero-day-exploit-adobe-flash-and-reader
http://community.websense.com/blogs/securitylabs/archive/2010/06/09/having-fun-with-adobe-0-day-exploits.aspx
http://secunia.com/advisories/40026
http://www.f-secure.com/weblog/archives/00001962.html
http://blogs.technet.com/srd/archive/2009/06/05/understanding-dep-as-a-mitigation-technology-part-1.aspx
http://blogs.technet.com/srd/archive/2009/06/12/understanding-dep-as-a-mitigation-technology-part-2.aspx

Credit

This vulnerability was reported by Will Dormann of the CERT/CC. It has also been independently discovered and exploited in the wild.

This document was written by Will Dormann.

Other Information

Date Public:	2010-06-04
Date First Published:	2010-06-07
Date Last Updated:	2010-06-18
CERT Advisory:
CVE-ID(s):	CVE-2010-1297
NVD-ID(s):	CVE-2010-1297
US-CERT Technical Alerts:
Metric:	43.09
Document Revision:	42