Title

Trust access for VBA must be disallowed. (Cat II impact)

Discussion

VSTO projects require access to the Visual Basic for Applications project system in Excel, PowerPoint, and Word, even though the projects do not use Visual Basic for Applications. Design-time support of controls in both Visual Basic and C# projects depends on the Visual Basic for Applications project system in Word and Excel. By default, Excel, Word, and PowerPoint do not allow automation clients to have programmatic access to VBA projects. Users can enable this by selecting the Trust access to the VBA project object model in the Macro Settings section of the Trust Center. However, doing so allows macros in any documents the user opens to access the core Visual Basic objects, methods, and properties, which represents a potential security hazard.

Check Content

The policy value for User Configuration -> Administrative Templates -> Microsoft Excel 2010 -> Excel Options -> Security -> Trust Center “Trust access to Visual Basic Project” must be set to “Disabled”. Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\14.0\excel\security Criteria: If the value AccessVBOM is REG_DWORD = 0, this is not a finding.

Fix Text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Excel 2010 -> Excel Options -> Security -> Trust Center “Trust access to Visual Basic Project” to “Disabled”.

Additional Identifiers

Rule ID: SV-33444r1_rule

Vulnerability ID: V-17522

Group Title: DTOO146-Disable Trust access to VB Project Macros

Expert Comments

CCIs tied to check.

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