Vulnerability in HTTP.sys Could Allow Remote Code Execution (3042553)
Published: April 14, 2015 | Updated: April 22, 2015
Version: 1.1
Executive Summary
This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow remote code execution if an attacker sends a specially crafted HTTP request to an affected Windows system.
This security update is rated Critical for all supported editions of Windows 7, Windows Server 2008 R2, Windows 8, Windows Server 2012, Windows 8.1, and Windows Server 2012 R2. For more information, see the Affected Software section.
The security update addresses the vulnerability by modifying how the Windows HTTP stack handles requests. For more information about the vulnerability, see the VulnerabilityInformation section.
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.
Note The update is available for Windows Technical Preview and Windows Server Technical Preview. Customers running these operating systems are encouraged to apply the update, which is available via Windows Update.
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 April bulletin summary.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
A remote code execution vulnerability exists in the HTTP protocol stack (HTTP.sys) that is caused when HTTP.sys improperly parses specially crafted HTTP requests. An attacker who successfully exploited this vulnerability could execute arbitrary code in the context of the System account.
To exploit this vulnerability, an attacker would have to send a specially crafted HTTP request to the affected system. The update addresses the vulnerability by modifying how the Windows HTTP stack handles requests.
Microsoft received information about this vulnerability through coordinated vulnerability disclosure. When this security bulletin was originally 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
The following workaround may be helpful in your situation:
Disable IIS kernel caching
This workaround is specific to IIS and can cause performance issues. For more information, see Enable Kernel Caching (IIS 7).
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 (April 14, 2015): Bulletin published.
V1.1 (April 22, 2015): Bulletin revised to correct the update replacement entries for Windows 8 and Windows Server 2012 in the Affected Software table. This is an informational change only. There were no changes to the update files. Customers who have already successfully updated their systems do not need to take any action.