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AUSCERT External Security Bulletin Redistribution
Microsoft Security Advisory 3050995 Improperly Issued
Digital Certificates Could Allow Spoofing
26 March 2015
AusCERT Security Bulletin Summary
Product: Microsoft Windows
Operating System: Windows Server 2003
Windows Server 2008
Windows Server 2008 R2
Windows Server 2012
Windows Server 2012 R2
Windows RT 8.1
Impact/Access: Provide Misleading Information -- Remote with User Interaction
Access Confidential Data -- Remote with User Interaction
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Microsoft Security Advisory 3050995 Improperly Issued Digital Certificates
Could Allow Spoofing
Published: March 24, 2015
Microsoft is aware of digital certificates that were improperly issued from
the subordinate CA, MCS Holdings, which could be used in attempts to spoof
content, perform phishing attacks, or perform man-in-the-middle attacks. The
improperly issued certificates cannot be used to issue other certificates,
impersonate other domains, or sign code. This issue affects all supported
releases of Microsoft Windows.
To help protect customers from the potentially fraudulent use of these
improperly issued certificates, Microsoft is updating the Certificate Trust
list (CTL) to remove the trust of the subordinate CA certificate. The trusted
root Certificate Authority, the China Internet Network Information Center
(CNNIC), has also revoked the certificate of the subordinate CA. Microsoft is
working on an update for Windows Server 2003 customers and will release it
once fully tested. For more information about these certificates, see the
Frequently Asked Questions section of this advisory.
Recommendation. Please see the Suggested Actions section of this advisory for
instructions on applying an update for specific releases of Microsoft Windows.
For more information about this issue, see the following references:
Microsoft Knowledge Base Article 3050995
This advisory discusses the following software.
Windows Server 2003 Service Pack 2
Windows Server 2003 x64 Edition Service Pack 2
Windows Server 2003 with SP2 for Itanium-based Systems
Windows Vista Service Pack 2
Windows Vista x64 Edition Service Pack 2
Windows Server 2008 for 32-bit Systems Service Pack 2
Windows Server 2008 for x64-based Systems Service Pack 2
Windows Server 2008 for Itanium-based Systems Service Pack 2
Windows 7 for 32-bit Systems Service Pack 1
Windows 7 for x64-based Systems Service Pack 1
Windows Server 2008 R2 for x64-based Systems Service Pack 1
Windows Server 2008 R2 for Itanium-based Systems Service Pack 1
Windows 8 for 32-bit Systems
Windows 8 for x64-based Systems
Windows Server 2012
Windows 8.1 for 32-bit Systems
Windows 8.1 for x64-based Systems
Windows Server 2012 R2
Windows RT 8.1
Server Core installation option
Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core
Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core
Windows Server 2008 R2 for x64-based Systems (Server Core installation)
Windows Server 2012 (Server Core installation)
Windows Server 2012 R2 (Server Core installation)
Windows Phone 8
Windows Phone 8.1
What is the scope of the advisory?
The purpose of this advisory is to notify customers that MCS Holdings
improperly issued SSL certificates for multiple sites including Google web
properties. These SSL certificates could be used to spoof content, perform
phishing attacks, or perform man-in-the-middle attacks against web properties.
The subordinate CA may also have been used to issue certificates for other,
currently unknown sites, which could be subject to similar attacks.
What caused the issue?
The issue was caused by MCS Holdings, a subordinate CA, improperly issuing
domain certificates to entities other than their owners. The MCS Holdings
authority is subordinated to the China Internet Network Information Center
(CNNIC), which is a CA present in the Trusted Root Certification Authorities
Does this update address any other digital certificates?
Yes, in addition to addressing the certificates described in this advisory,
this update is cumulative and includes digital certificates described in
Microsoft Security Advisory 3046310
Microsoft Security Advisory 2982792
Microsoft Security Advisory 2916652
Microsoft Security Advisory 2798897
Microsoft Security Advisory 2728973
Microsoft Security Advisory 2718704
Microsoft Security Advisory 2641690
Microsoft Security Advisory 2607712
Microsoft Security Advisory 2524375
What is cryptography?
Cryptography is the science of securing information by converting it between
its normal, readable state (called plaintext) and one in which the data is
obscured (known as ciphertext).
In all forms of cryptography, a value known as a key is used in conjunction
with a procedure called a crypto algorithm to transform plaintext data into
ciphertext. In the most familiar type of cryptography, secret-key
cryptography, the ciphertext is transformed back into plaintext using the same
key. However, in a second type of cryptography, public-key cryptography, a
different key is used to transform the ciphertext back into plaintext.
What is a digital certificate?
In public-key cryptography, one of the keys, known as the private key, must be
kept secret. The other key, known as the public key, is intended to be shared
with the world. However, there must be a way for the owner of the key to tell
the world who the key belongs to. Digital certificates provide a way to do
this. A digital certificate is a tamperproof piece of data that packages a
public key together with information about it (who owns it, what it can be
used for, when it expires, and so forth).
What are certificates used for?
Certificates are used primarily to verify the identity of a person or device,
authenticate a service, or encrypt files. Normally you wont have to think
about certificates at all. You might, however, see a message telling you that
a certificate is expired or invalid. In those cases you should follow the
instructions in the message.
What is a certification authority (CA)?
Certification authorities are the organizations that issue certificates. They
establish and verify the authenticity of public keys that belong to people or
other certification authorities, and they verify the identity of a person or
organization that asks for a certificate.
What is a Certificate Trust List (CTL)?
A trust must exist between the recipient of a signed message and the signer of
the message. One method of establishing this trust is through a certificate,
an electronic document verifying that entities or persons are who they claim
to be. A certificate is issued to an entity by a third party that is trusted
by both of the other parties. So, each recipient of a signed message decides
if the issuer of the signer's certificate is trustworthy. CryptoAPI has
implemented a methodology to allow application developers to create
applications that automatically verify certificates against a predefined list
of trusted certificates or roots. This list of trusted entities (called
subjects) is called a certificate trust list (CTL). For more information,
please see the MSDN article, Certificate Trust Verification.
What might an attacker do with these certificates?
An attacker could use these certificates to spoof content, perform phishing
attacks, or perform man-in-the-middle attacks against the following web
What is a man-in-the-middle attack?
A man-in-the-middle attack occurs when an attacker reroutes communication
between two users through the attackers computer without the knowledge of the
two communicating users. Each user in the communication unknowingly sends
traffic to and receives traffic from the attacker, all the while thinking they
are communicating only with the intended user.
What is Microsoft doing to help with resolving this issue?
Although this issue does not result from an issue in any Microsoft product, we
are nevertheless updating the CTL and providing an update to help protect
customers. Microsoft will continue to investigate this issue and may make
future changes to the CTL or release a future update to help protect
After applying the update, how can I verify the certificates in the Microsoft
Untrusted Certificates Store?
For Windows Vista, Windows 7, Windows Server 2008, and Windows Server 2008 R2
systems that are using the automatic updater of revoked certificates (see
Microsoft Knowledge Base Article 2677070 for details), and for Windows 8,
Windows 8.1, Windows RT, Windows RT 8.1, Windows Server 2012, and Windows
Server 2012 R2 systems, you can check the Application log in the Event Viewer
for an entry with the following values:
Event ID: 4112
Description: Successful auto update of disallowed certificate list with
effective date: Monday, March 23, 2015 (or later).
For systems not using the automatic updater of revoked certificates, in the
Certificates MMC snap-in, verify that the following certificate has been added
to the Untrusted Certificates folder:
Certificate Issued by Thumbprint
MCSHOLDING TEST CNNIC ROOT e1 f3 59 1e 76 98 65 c4 e4 47 ac c3 7e af c9 e2 bf e4 c5 76
Note For information on how to view certificates with the MMC Snap-in, see the
MSDN article, How to: View Certificates with the MMC Snap-in.
Apply the update for supported releases of Microsoft Windows
An automatic updater of revoked certificates is included in supported editions
of Windows 8, Windows Server 2012, Windows RT, Windows 8.1, Windows RT 8.1,
and Windows Server 2012 R2, and for devices running Windows Phone 8 and
Windows Phone 8.1. For these operating systems or devices, customers do not
need to take any action, because the CTL will be updated automatically.
For systems running Windows Vista, Windows 7, Windows Server 2008, or Windows
Server 2008 R2 that are using the automatic updater of revoked certificates
(see Microsoft Knowledge Base Article 2677070 for details), customers do not
need to take any action, because these systems will be automatically
Additional Suggested Actions
Protect your PC
We continue to encourage customers to follow our Protect Your Computer
guidance of enabling a firewall, getting software updates and installing
antivirus software. For more information, see Microsoft Safety & Security
Keep Microsoft Software Updated
Users running Microsoft software should apply the latest Microsoft
security updates to help make sure that their computers are as protected as
possible. If you are not sure whether your software is up to date, visit
Microsoft Update, scan your computer for available updates, and install any
high-priority updates that are offered to you. If you have automatic updating
enabled and configured to provide updates for Microsoft products, the updates
are delivered to you when they are released, but you should verify that they
You can provide feedback by completing the Microsoft Help and Support
form, Customer Service Contact Us.
Customers in the United States and Canada can receive technical support
from Security Support. For more information, see Microsoft Help and Support.
International customers can receive support from their local Microsoft
subsidiaries. For more information, see International Support.
Microsoft TechNet Security provides additional information about security in
The information provided in this advisory 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 (March 24, 2015): Advisory published.
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