Title

Do not allow choice of output to include PNG (Portable Network Graphics) (Cat III impact)

Discussion

Excel 2007, PowerPoint 2007, and Word 2007 can save graphic files in Portable Network Graphics (PNG) format to improve the quality of the graphics when documents are saved as Web pages. The PNG graphic file format (.png) is used for a wide range of graphics, from small images (such as bullets and banners) to complex images (such as photographs), and can offer better image fidelity and smaller file sizes than some other formats. However, PNG graphics cannot be displayed by many earlier Web browsers, such as Microsoft Internet Explorer® version 5 or earlier. By default, Office applications do not save graphics in the PNG format. To change this functionality, users can open the application's Options dialog box, click Advanced, click Web Options, and then select the Allow PNG as a graphics format check box. This setting can be used to guard against theoretical future zero-day attacks that might target PNG files.

Check Content

The policy value for User Configuration -> Administrative Templates -> Microsoft Office 2007 system -> Tools \ Options \ General \ Web Options -> Browsers “Allow PNG as an output format” will be set to “Disabled”. Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\12.0\Common\Internet Criteria: If the value AllowPNG is REG_DWORD = 0, this is not a finding.

Fix Text

The policy value for User Configuration -> Administrative Templates -> Microsoft Office 2007 system -> Tools \ Options \ General \ Web Options -> Browsers “Allow PNG as an output format” will be set to “Disabled”. "Note: Group Policy Administrative Templates are available from the www.microsoft.com download site. The MS Office 2007 System (Office12.adm) is included in the AdminTemplates.exe file. This template provides the mechanisms to incorporate Microsoft Office 2007 System policies via the Microsoft Group Policy Editor (gpedit.msc)." "Note: If the Microsoft Group Policy Editor (gpedit.msc) is not used to incorporate the remediation to this vulnerability the Microsoft Registry Editor (regedit.exe) may be used to create the registry key and value required."

Additional Identifiers

Rule ID: SV-18661r1_rule

Vulnerability ID: V-17561

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.