VM Deployment

Question

VM Deployment

Jeffrey Cummings 0

Unable to create any VM resources

All deployment attempts fail with:

HTTP Error 400

Bad Request - Request Too Long

The size of the request headers is too long.

Occurs in:

Azure Portal
Azure Cloud Shell (CLI)

Tested with:

Ubuntu 24.04

Standard_D2s_v3

Region: East US 2

Also attempted in Central US.

Deployment fails before resource provisioning begins.

Suspected ARM request header / token size issue or tenant authentication problem.

Please investigate why ARM requests from this tenant are returning "Request Too Long".

Jilakara Hemalatha 10,365 Reputation points Microsoft External Staff Moderator

2026-03-12T23:16:35.7+00:00
Hello

Thank you for reaching out. To better understand the issue, could you please provide the following details:

How many Azure AD / Entra ID groups is your account currently a member of? You can check this by going to Entra ID → Users → Your Name → Groups and counting the total.

Are you using a personal user account, a service principal, or a managed identity to perform these deployments? Has this deployment worked successfully before, or is this your first attempt?

Is this issue affecting only your account, or are other users in the same tenant also unable to deploy VM resources?

Have there been any recent changes to your account, such as being added to new AD groups, new RBAC role assignments, or any tenant-level policy changes around the time this issue started?

Can you run the following command in Cloud Shell and share the character count or full output of your current token so we can confirm if token size is the root cause? az account get-access-token --query accessToken -o tsv | wc -c

Have there been any recent changes to your tenant’s security settings, group memberships, or role assignments?
Jilakara Hemalatha 10,365 Reputation points Microsoft External Staff Moderator

2026-03-13T00:01:29.8+00:00
Also, could you please check if there are any ARM deployment logs available for the failed attempts?

You can do this by:

Opening the Azure Portal → Resource Groups → [Target Resource Group] → Deployments.

Click on the failed deployment to view the detailed error message and operations.

Share the error details or screenshots with us so we can confirm if the issue is coming from the request headers or token size.

If you prefer using CLI, you can also run:

az deployment group show --resource-group <ResourceGroupName> --name <DeploymentName>

and share the full output of the failed deployment.