MS15-105 – Vulnerability in Windows Hyper-V Could Allow Security Feature Bypass

Microsoft released a security hotfix for Hyper-V last night. They describe it as:

This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow security feature bypass if an attacker runs a specially crafted application that could cause Windows Hyper-V to incorrectly apply access control list (ACL) configuration settings. Customers who have not enabled the Hyper-V role are not affected.

This security update is rated Important for all supported editions of Windows 8.1 for x64-based Systems, Windows Server 2012 R2, and Windows 10 for x64-based Systems. For more information, see the Affected Software section.

The security update addresses the vulnerability by correcting how Hyper-V applies ACL configuration settings. For more information about the vulnerability, see the Vulnerability Information section.

KB3091287 does go into any more detail.

CVE-2015-2534 simply says:

Hyper-V in Microsoft Windows 8.1, Windows Server 2012 R2, and Windows 10 improperly processes ACL settings, which allows local users to bypass intended network-traffic restrictions via a crafted application, aka “Hyper-V Security Feature Bypass Vulnerability.”

Affected OSs are:

  • Windows 10
  • Windows 8.1
  • Windows Server 2012 R2

No Windows 8 or WS2012 – that makes me wonder if this is something to do with Extended Port ACLs.

Credit: Patrick Lownds (MVP) for tweeting the link.

Microsoft News – 7 September 2015

Here’s the recent news from the last few weeks in the Microsoft IT Pro world:


Windows Server


System Center


Office 365



  • Meet AzureCon: A virtual event on Azure on September 29th, starting at 9am Pacific time, 5pm UK/Irish time.

MS15-068–SERIOUS Hyper- V Security Vulnerability

This is one of those rare occasions where I’m going to say: put aside everything you are doing, test this MS15-068 patch now, and deploy it as soon as possible.

The vulnerabilities could allow remote code execution in a host context if a specially crafted application is run by an authenticated and privileged user on a guest virtual machine hosted by Hyper-V. An attacker must have valid logon credentials for a guest virtual machine to exploit this vulnerability.

This security update is rated Critical for Windows Hyper-V on Windows Server 2008, Windows Server 2008 R2, Windows 8 and Windows Server 2012, and Windows 8.1 and Windows Server 2012 R2. For more information, see the Affected Software section.

The security update addresses the vulnerabilities by correcting how Hyper-V initializes system data structures in guest virtual machines.

I don’t know if this is definitely what we would call a “breakout attack” (I’m awaiting confirmation), one where a hacker in a compromised VM can reach out to the host, but it sure reads like it. This makes it the first one of these that I’ve heard of in the life of Hyper-V (since beta of W2008) – VMware fanboys, you’ve had a few of these so be quiet.


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.

It sounds like a reasonable organization found and privately disclosed this bug, thus allowing Microsoft to protect their customers before it became public knowledge. Google could learn something here.

So once again:

  1. Test the patch quickly
  2. Push it out to secure hosts and other VMs


Some digging by Flemming Riis (MVP) discover that credit goes to Thomas Garnier, Senior Security Software Development Engineer at Microsoft (a specialty in kernel, hypervisor, hardware, cloud and network security), and currently working on Azure OS (hence the Hyper-V interest, I guess). He is co-author of Sysinternals Sysmon with Mark Russinovich.


Software-Defined Storage Calculator and Design Considerations Guide

Microsoft has launched an Excel-based sizing tool to help you plan Storage Spaces (Scale-Out File Server) and guidance on how to design your Storage Spaces deployments.

Here’s the sizing for a very big SOFS that will require 4 x SOFS server nodes and 4 x 60 disk JBODs:

image The considerations guide will walk you through using the sizing tool.

Some updates are required – some newer disk sizes aren’t included – but this is a great starting point for a design process.

Microsoft News – 29 June 2015

As you might expect, there’s lots of Azure news. Surprisingly, there is still not much substantial content on Windows 10.


Windows Server

Windows Client



Office 365



Microsoft News 28-May-2015

Very little to cover here, except one possibly controversial article on Hyper-V that you long-time readers might expect me to write an angry response to …


Windows Server


Office 365

Microsoft News – 25-May-2015

It’s taken me nearly all day to fast-read through this lot. Here’s a dump of info from Build, Ignite, and since Ignite. Have a nice weekend!


Windows Server

Windows Client

System Center


Office 365


  • Announcing support for Windows 10 management with Microsoft Intune: Microsoft announced that Intune now supports the management of Windows 10. All existing Intune features for managing Windows 8.1 and Windows Phone 8.1 will work for Windows 10.
  • Announcing the Mobile Device Management Design Considerations Guide: If you’re an IT Architect or IT Professional and you need to design a mobile device management (MDM) solution for your organization, there are many questions that you have to answer prior to recommending the best solution for the problem that you are trying to solve. Microsoft has many new options available to manage mobile devices that can match your business and technical requirements.
  • Mobile Application Distribution Capabilities in Microsoft Intune: Microsoft Intune allows you to upload and deploy mobile applications to iOS, Android, Windows, and Windows Phone devices. In this post, Microsoft will show you how to publish iOS apps, select the users who can download them, and also show you how people in your organization can download these apps on their iOS devices.
  • Microsoft Intune App Wrapping Tool for Android: Use the Microsoft Intune App Wrapping Tool for Android to modify the behavior of your existing line-of-business (LOB) Android apps. You will then be able to manage certain app features using Intune without requiring code changes to the original application.



My Microsoft Ignite 2015 Session Content

Microsoft recorded and shared a video of my session, The Hidden Treasures of Windows Server 2012 R2 Hyper-V, along with the slides.

My second session, End to-End Azure Site Recovery Solutions for Small-Medium Enterprises in one of the community theatres, was not recorded so I have placed the slides up on slideshare.

Ignite 2015 – Spaces-Based, Software-Defined Storage–Design and Configuration Best Practices

Speakers: Joshua Adams and Jason Gerend, Microsoft.

Designing a Storage Spaces Solution

  1. Size your disks for capacity and performance
  2. size your storage enclosures
  3. Choose how to handlw disk failures
  4. Pick the number of cluster nodes
  5. Select a hardware solution
  6. Design your storage pools
  7. Design your virtual disks

Size your disks – for capacity (HDDs)

  1. Identify your workloads and resiliency type: Parity for backups and mirror for everything else.
  2. Estimate how much raw capacity you need. Currently capcity x% data grown X data copies (if your using mirrors). Add 12% initially for automatic virtual disk repairs and meta data overhead. Example: 135 TB x 1. x 3 data copies + 12 % = 499 TB raw capacity
  3. Size your HDDs: Pick big 7200 RPM NL SAS HDDs. Fast HDD not required is using SSD tier.

Software Defined Storage Calculator allows you to size and design a deployment and it generates the PowerShell. Works with WS2012 R2 and WS2016, disaggregated and hyperconverged deployments.

Size your disks – for performance (SSDs)

  1. How many SSDs to use. Sweet spot is 1 SSD for every 2-4 HDDs. Typically 4-5 SSDs per enclosure per pool. More SSDs = more absolute performance
  2. Determine the SD size. 800 GB SSDs are typical. Larger SSD capacity = can handle larger amounts of active data. Anticipate around 10% of SSD capacity for automatically repairing after an SSD failure.

Example 36 x 800 GB SSDs.

Size you Enclosures

  1. Pick the enclosure size (12, 24, 60, etc  disks)
  2. Pick the number of enclosures. If you have 3 or 4 then you have enclosure awareness/fault tolerance, depending on type of mirroring.
  3. Each enclosure should have an identical number of disks.

Example, 3 x 60 bay JBODs each with 48 HDDs and 12 SSDs

The column count is fixed between 2 tiers. The smaller tier (SSD) limits the column count. 3-4 columns is a sweet spot.

Expanding pools has an overhead. Not trivial but it works. Recommend that you fill JBODs.

Choose how to Handle Disk Failures

  1. Simultaneous disk failures to tolerate. Use 2 data copies for small deployments and disks, and/or less important data. use 3 data copies for larger deployments and disks, and for more important data.
  2. Plan to automatically repair disks. Instead of hot spares, set aside pool capacity to automatically replace failed disks. Also effects column count … more later.

Example: 3-way mirrors.

Pick the number of Cluster Nodes

Start with 1 node per enclosure and scale up/down depending on the amount of compute required. This isn’t about performance; it’s about how much compute you can afford to lose and still retain HA.

Example: 3 x 3 = 3 SOFS nodes + 3 JBODs.

Select a hardware vendor

  1. DataON
  2. Dell
  3. HP
  4. RAID Inc
  5. Microsoft/Dell CPS

Design your Storage Pools

  1. Management domains: put your raw disks in the pool and manage them as a group. Some disk settings are applied at the pool level.
  2. More pools = more to manage. Pools = fault domains. More pools = less risk – increased resiliency and resiliency overhead..

Start with 84 disks per pool.

Divide disks evenly between pools.

Design your Virtual Disks

  • Where storage tiers, write-back cache and enclosure awareness are set.
  • More VDs = more uniform load balancing, but more to manage.
  • This is where column count come in. More columns = more throughput, but more latency. 3-4 columns is best.
  • Load balancing is dependent on identical virtual disks.
  • To automatically repair after a disk failure, need at least one more disk per tier than columns for the smallest tier, which is usually the SSD tier.
  1. Set aside 10% of SSD and HDD capacity for repairs.
  2. Start with 2 virtual disks per node.
  3. Add more to keep virtual disk size to 10 TB or less. Divide SSD and HDD capacity evenly between virtual disks. Use 3-4 columns if possible.

Best Practices for WS2012 R2

  • Scale by adding fully populated clusters. Get used to the concept of storage/compute/networking stamps.
  • Monitor your existing workloads for performance. The more you know about the traits of your unique workloads, the better future deployments will be.
  • Do a PoC deployment. Use DiskSpd and fault injection to stress the solution. Monitor the storage tiers performance to determine how much SSD capacity you need to fit a given scale of your workloads into SSD tiers.

WORK WITH A TRUSTED SOLUTION VENDOR. Not all hardware is good, even if it is on the HCL. Some are better than others, and some suck. In my opinion Intel and Quanta suck. DataON is excellent. Dell appears to have gone through hell during CPS development to be OK. And some disks, e.g. SanDISK, are  the spawn of Satan, in my experience – Note that Dell use SanDISK and Toshiba so demand Toshiba only SSDs from Dell. HGST SSDs are excellent.

Deployment Best Practices

  • Disable TRIM on SSDs. Some drives degrade performance with TRIM enabled.
  • Disable all disk based caches – if enabled if degrades performance when write-through is used (Hyper-V).
  • Use LB (least blocks) for MPIO policy. For max performance, set individual SSDs to Round Robin. This must be done on each SOFS node.
  • Optimize Storage Spaces repair settings on SOFS. Use Fast Rebuild. Change it from Auto to Always on the pool. This means that 5 minutes after a write failure, a rebuild will automatically start. Pulling a disk does not trigger an automatic rebuild – an expensive process.
  • Install the latest updates. Example: repair process got huge improvement in November 2014 update.

Deployment & Management Best Practices

  • Deploy using VMM or PowerShell. FCM is OK for small deployments.
  • VMM is great for some stuff, but in 2012 R2 it doesn’t do tiering etc. It can create the cluster well and manage shares, but for disk creation, use PowerShell.
  • Monitor it using SCOM with the new Storage Spaces management pack.
  • Also use Test-StorageHealth.PS1 to do some checks occasionally. It needs tweaking to size it for your configuration.

Design Closing Thoughts

  • Storage Spaces solutions offer: 2-4 cluster nodes and 1-4 JBODs. Store 100 to as many as 2000 VMs.
  • Storage Pool Design; HDDs  provide most of the capacity. SSDs offer performance. Up to 84 disks per pool.
  • Virtual Disk design: Set aside 10% of SSD and HDD capacity for repairs. Start with 2 VDs per node. Max 0 TB/virtual disk. 3-4 volums for balanced performance.

Coming in May

  • Storage Spaces Design Considerations Guide (basis of this presentation)
  • Storage Spaces Design Calculator (spreadsheet used in this presentation)

All The Details On My Two Ignite Sessions

Thanks (I think!!!) to John at MicroWarehouse (my employer) for sticking this on the company website:


I think he even Photoshop slimmed me Smile

Here’s the details of both my sessions:

The Hidden Treasures of Windows Server 2012 R2 Hyper-V

  • When: 5:00PM – 6:15PM, Tuesday, May 5th
  • Where: E451A
  • Session code: BRK3506

My first session is a 75 minute level 300 session focusing on lesser known features of the version of Hyper-V that you can deploy now, and leaves you in the best position to upgrade to vNext. Don’t worry if you’ve seen by TEE14 session; this one is 50% different with some very useful stuff that I’ve never presented on or blogged about before.

It’s one thing to hear about and see a great demo of a Hyper-V feature. But how do you put them into practice? This session takes you through some of those lesser-known elements of Hyper-V that have made for great demonstrations, introduces you to some of the lesser-known features, and shows you best practices, how to increase serviceability and uptime, and design/usage tips for making the most of your investment in Hyper-V.


End-to-End Azure Site Recovery Solutions for Small & Medium Enterprises

  • When: 12:05PM – 12:25PM, Thursday, May 7th
  • Where: EXPO: Lounge C Theater
  • Session Code: THR0903

My second session is 20 minutes on Azure DR solutions for SMEs in the community theatre. I’ve done lots of lab and proof-of-concept work with ASR in the SME space and this presentation focuses on the stuff that no one talks about – it’s easy to replicate VMs, but what about establishing services, accessing failed over VMs, and more?!?!?

In this session I will share some tips and lessons that I have learned from working with Azure Site Recovery services to provide a complete disaster recovery solution in Azure for Hyper-V virtual machines in a small/medium enterprise.