Microsoft Security Bulletin MS14-066 – Critical November 11, 2014

This security update resolves a privately reported vulnerability in the Microsoft Secure Channel (Schannel) security package in Windows. The vulnerability could allow remote code execution if an attacker sends specially crafted packets to a Windows server.

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

The security update addresses the vulnerability by correcting how Schannel sanitizes specially crafted packets. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability.

For more information about this update, see Microsoft Knowledge Base Article 2992611.

The following software has been tested to determine which versions or editions are affected. Other versions or editions 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.

Affected Software

[1]This update is available via Windows Update only.

Does this update contain any additional security-related changes to functionality?
Yes. In addition to the changes that are listed in the Vulnerability Information section of this bulletin, this update includes changes to available TLS cipher suites. This update includes new TLS cipher suites that offer more robust encryption to protect customer information. These new cipher suites all operate in Galois/counter mode (GCM), and two of them offer perfect forward secrecy (PFS) by using DHE key exchange together with RSA authentication.

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 November bulletin summary.

Microsoft Schannel Remote Code Execution Vulnerability – CVE-2014-6321

A remote code execution vulnerability exists in the Secure Channel (Schannel) security package due to the improper processing of specially crafted packets. 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. The update addresses the vulnerability by correcting how Schannel sanitizes specially crafted packets.

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

FAQ

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could run arbitrary code on a target server.

How could an attacker exploit the vulnerability?
An attacker could attempt to exploit this vulnerability by sending specially crafted packets to a Windows server.

What systems are primarily at risk from the vulnerability?
Server and workstation systems that are running an affected version of Schannel are primarily at risk.

For Security Update Deployment information, see the Microsoft Knowledge Base article “Microsoft Security Bulletin MS14-066 – Critical” in the Executive Summary.

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

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.

• V1.0 (November 11, 2014): Bulletin published.