Microsoft Security Bulletin MS15-074 - Important

Vulnerability in Windows Installer Service Could Allow Elevation of Privilege (3072630)

Published: July 14, 2015 | Updated: July 29, 2015

Version: 2.0

Executive Summary

This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow elevation of privilege if the Windows Installer service improperly runs custom action scripts. An attacker must first compromise a user who is logged on to the target system to exploit the vulnerability. An attacker could then install programs; view, change, or delete data; or create new accounts with full administrative rights.

This security update is rated Important for all supported editions of Microsoft Windows. For more information, see the Affected Software section.

The security update addresses the vulnerability by correcting how custom action scripts are executed. For more information about the vulnerability, see the Vulnerability Information section.

For more information about this update, see Microsoft Knowledge Base Article 3072630.

Affected Software

The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

^[1]This update is for systems that have the 3072630 update installed. See the UpdateFAQ for more information.

^[2]This update is available via Windows Update only.

*The Updates Replaced column shows only the latest update in a chain of superseded updates. For a comprehensive list of updates replaced, go to the Microsoft Update Catalog, search for the update KB number, and then view update details (updates replaced information is on the Package Details tab).

FAQ

I am running Windows Server 2003 and install updates manually. Are there any prerequisites for installing the 3072630 update?
Yes. Customers who are running Windows Server 2003 and who install updates manually must install Windows Installer 4.5 before installing the 3072630 update. Windows Installer 4.5 will be installed automatically for customers who have automatic updating enabled. For more information about the prerequisite Installer update, see Microsoft Knowledge Base Article 942288.

Severity Ratings and Vulnerability Identifiers

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the July bulletin summary.

Vulnerability Information

Windows Installer EoP Vulnerability - CVE-2015-2371

An elevation of privilege vulnerability exists in some cases in the Windows Installer service when it improperly runs custom action scripts. An attacker who successfully exploited this vulnerability could elevate privileges on a targeted system. An attacker could then install programs; view, change, or delete data; or create new accounts with full administrative rights.

To exploit the vulnerability, an attacker must first compromise a user who is logged on to the target system, then find a vulnerable .msi package that is installed on the target system and, finally, place specially crafted code on the target system that the vulnerable .msi package can execute.

Microsoft received information about this vulnerability through coordinated vulnerability disclosure. When this security bulletin was issued, Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers.

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Security Update Deployment

For Security Update Deployment information, see the Microsoft Knowledge Base article referenced in the Executive Summary.

Acknowledgments

Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgments for more information.

Disclaimer

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions

• V1.0 (July 14, 2015): Bulletin published.
• V2.0 (July 29, 2015): Bulletin rereleased to announce the availability of an update package for Windows 10 systems. Customers running Windows 10 should apply the 3074683 update to be protected from the vulnerability discussed in this bulletin. The update is available via Windows Update only. The majority of customers have automatic updating enabled and will not need to take any action because the update will be downloaded and installed automatically.

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