May 18, 2018

Unable to RDP into Azure VMs

After patching all the Windows Server in Azure, a colleague calls me in panic, because their users, could not access their VMs through RDP. They were getting a CredSSP error (picture bellow).

 So, after reading the link bellow, it seems it could be related with the March update.

https://support.microsoft.com/en-us/help/4093492/credssp-updates-for-cve-2018-0886-march-13-2018

Rebooting the VM didn’t sort the issue, there’s a few mitigations listed in this post

https://blogs.technet.microsoft.com/mckittrick/unable-to-rdp-to-virtual-machine-credssp-encryption-oracle-remediation/

Then I realize that was a simple solution for an organization. What about all of those situations that your Azure VM is not domain join, like “Jump Servers”? I’m wondering if you have a single VM in a subscription for whatever reason, and a Windows update or any other issue blocks RDP because security issues, what’s the recommended way to connect to such a virtual machine?

One of the first things you should try is to disable the NLA, you can try to do it following these steps:

1. Open regedit on another virtual machine on the same network.
2. Under the File menu click “Connect Network Registry…”
3. Enter your computer name and click Ok.  If this fails to connect you try the way through command line (see the post How to remotely disable Network Level Authentication (NLA) on Azure Virtual Machine)  
4. Scroll down in the left pane to find the newly added server. Navigate to this Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp
5. Find the value “SecurityLayer” and change the data to 0
6. Try to RDP. In case of failure, reboot the VM and try again.

Cheers,

Marcos Nogueira
Azure MVP
azurecentric.com
Twitter: @mdnoga

Written by Marcos Nogueira

Marcos Nogueira

With more than 18 years experience in Datacenter Architectures, Marcos Nogueira is currently working as a Principal Cloud Solution Architect. He is an expert in Private and Hybrid Cloud, with a focus on Microsoft Azure, Virtualization and System Center. He has worked in several industries, including Aerospace, Transportation, Energy, Manufacturing, Financial Services, Government, Health Care, Telecoms, IT Services, and Gas & Oil in different countries and continents. Marcos was a Canadian MVP in System Center Cloud & Datacenter Managenment and he has +14 years as Microsoft Certified, with more than 100+ certifications (MCT, MCSE, and MCITP, among others). Marcos is also certified in VMware, CompTIA and ITIL v3. He assisted Microsoft in the development of workshops and special events on Private & Hybrid Cloud, Azure, System Center, Windows Server, Hyper-V and as a speaker at several Microsoft TechEd/Ignite and communities events around the world.

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Marcos Nogueira

With more than 18 years experience in Datacenter Architectures, Marcos Nogueira is currently working as a Principal Cloud Solution Architect. He is an expert in Private and Hybrid Cloud, with a focus on Microsoft Azure, Virtualization and System Center. He has worked in several industries, including Aerospace, Transportation, Energy, Manufacturing, Financial Services, Government, Health Care, Telecoms, IT Services, and Gas & Oil in different countries and continents. Marcos was a Canadian MVP in System Center Cloud & Datacenter Managenment and he has +14 years as Microsoft Certified, with more than 100+ certifications (MCT, MCSE, and MCITP, among others). Marcos is also certified in VMware, CompTIA and ITIL v3. He assisted Microsoft in the development of workshops and special events on Private & Hybrid Cloud, Azure, System Center, Windows Server, Hyper-V and as a speaker at several Microsoft TechEd/Ignite and communities events around the world.

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