US-CERT Technical Cyber Security Alert TA10-159A -- Adobe Flash, Reader, and Acrobat Vulnerability

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National Cyber Alert System

Technical Cyber Security Alert TA10-159A

Adobe Flash, Reader, and Acrobat Vulnerability

Original release date: June 08, 2010
Last revised: --
Source: US-CERT

Systems Affected

* Adobe Flash Player and earlier 10.x versions
* Adobe Flash Player 9.0.262 and earlier 9.x versions
* Adobe Reader 9.3.2 and earlier 9.x versions
* Adobe Acrobat 9.3.2 and earlier 9.x versions

Other Adobe products that support Flash may also be vulnerable.


According to Adobe, there is a vulnerability in Adobe Flash. This
vulnerability affects Flash Player, Reader, Acrobat, and possibly
other products that support Flash. A remote attacker could exploit
this vulnerability to execute arbitrary code.

I. Description

Adobe Security Advisory APSA10-01 describes a vulnerability in
Adobe Flash that affects Flash Player, Reader, and Acrobat. It may
also affect other products that independently support Flash, such
as Photoshop, Photoshop Lightroom, Freehand MX, and Fireworks.

An attacker could exploit this vulnerability by convincing a user
to open specially crafted Flash content. Flash content is commonly
hosted on a web page, but it can also be embedded in PDF and other
documents or provided as a stand-alone file.

As noted in APSA10-01, "There are reports that this vulnerability
is being actively exploited in the wild against both Adobe Flash
Player, and Adobe Reader and Acrobat."

Additional information is available in US-CERT Vulnerability Note

II. Impact

If a user opens specially crafted Flash content, a remote attacker
may be able to execute arbitrary code.

III. Solution


Adobe Security Advisory APSA10-01 suggests updating to the release
candidate of Flash Player 10.1.

Disable Flash in your web browser

Uninstall Flash or restrict which sites are allowed to run Flash.
To the extent possible, only run trusted Flash content on trusted
domains. For more information, see Securing Your Web Browser.

Disable Flash in Adobe Reader and Acrobat

Disabling Flash in Adobe Reader will mitigate attacks that rely on
Flash content 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, delete, rename, or remove
access to these files:

Microsoft Windows

"%ProgramFiles%\Adobe\Reader 9.0\Reader\authplay.dll"
"%ProgramFiles%\Adobe\Reader 9.0\Reader\rt3d.dll"

Apple Mac OS X

"/Applications/Adobe Reader 9/Adobe"
"/Applications/Adobe Reader 9/Adobe"

GNU/Linux (locations may vary among distributions)


File locations may be different for Adobe Acrobat or other Adobe
products that include Flash and 3D & Multimedia support. Disabling
these plugins will reduce functionality and will not protect
against Flash content 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.

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 a safer option that
prompts the user by importing the following as a .REG file:

Windows Registry Editor Version 5.00


Disable the display of PDF documents in the web browser

Preventing PDF documents from opening inside a web browser will
partially mitigate this vulnerability. If this workaround is
applied, it may also mitigate future vulnerabilities.

To prevent PDF documents from automatically being opened in a web
browser, do the following:

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.

Disable JavaScript in Adobe Reader and Acrobat

Disabling JavaScript provides some additional protection against
attacks. Acrobat JavaScript can be disabled using the Preferences
menu (Edit -> Preferences -> JavaScript; uncheck Enable Acrobat

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.

Do not access PDF documents from untrusted sources

Do not open unfamiliar or unexpected PDF documents, particularly
those hosted on websites or delivered as email attachments. Please
see Cyber Security Tip ST04-010.

IV. References

* Security Advisory for Flash Player, Adobe Reader and Acrobat -

* Adobe Labs - Flash Player 10 pre-release -

* US-CERT Vulnerability Note VU#486225 -

* Securing Your Web Browser -

* Understanding DEP as a mitigation technology part 1 -

* Understanding DEP as a mitigation technology part 2 -


The most recent version of this document can be found at:


Feedback can be directed to US-CERT Technical Staff. Please send
email to <cert@xxxxxxxx> with "TA10-159A Feedback VU#486225" in
the subject.

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Revision History

June 08, 2010: Initial release

Version: GnuPG v1.4.5 (GNU/Linux)