Windows Server 2025 (26100): vmicvss fails to start with Event 7009 connect timeout on multiple guests - production checkpoints and backups broken

Emran Moradian 0 Reputation points
2026-07-01T21:28:37.4866667+00:00

Environment:

  • Host: Windows Server 2025 Standard, build 26100, standalone (workgroup)
  • Guests: 2x Windows Server 2025, VM config version 12.0 (one Domain Controller, one File Server)
  • Updates: KB5094137, KB5094125 (June 2026 CUs), KB5087051

Problem:

The Hyper-V Volume Shadow Copy Requestor service (vmicvss) fails to start inside BOTH guest VMs. This breaks production checkpoints and all application-consistent backups.

Symptoms:

  • vmicvss is Stopped; manual start fails with Error 1053
  • SCM Event 7000 + 7009: "A timeout was reached (30000 ms) while waiting for the Hyper-V Volume Shadow Copy Requestor service to connect." PID stays 0
  • From host, Get-VMIntegrationService shows VSS = "No Contact" on both VMs; all other integration services (Heartbeat, Shutdown, KVP, Time Sync) = OK
  • Manual production checkpoint fails on the host: Set-VM -CheckpointType ProductionOnly + Checkpoint-VM returns "Production checkpoints cannot be created" (VMMS Event 18012 / 18016)

Diagnostics already completed - ALL verified healthy:

  • VMBus driver loaded (guest wvmbus.inf, host wvmbusr.inf); VSS VMBus channel present
  • Device Manager: "Microsoft Hyper-V Volume Shadow Copy" = Status OK
  • Registry verified correct: ImagePath (svchost -k LocalSystemNetworkRestrictedRedirectionGuard -p), ServiceDll (icsvcvss.dll), ServiceMain (VSSServiceMain), Start=3
  • icsvcvss.dll present and healthy (v10.0.26100.1)
  • SFC /scannow = clean; DISM /RestoreHealth = clean
  • vssadmin list writers = all Stable / No error (both guests AND host, including Microsoft Hyper-V VSS Writer)
  • pnputil device remove + rescan of the VSS integration device did NOT resolve it
  • Full guest reboots and Disable/Enable of VSS integration did NOT resolve it

Key point:

Both independent VMs show identical behavior, and the failure reproduces on the host independently of any backup software. The vmicvss connect timeout (Event 7009, PID 0) with every component verified healthy suggests a Hyper-V integration-component regression in build 26100, possibly related to the June 2026 cumulative updates.

Questions:

  1. Is this a known issue on Windows Server 2025 build 26100?
  2. Is there a hotfix, out-of-band update, or workaround?
  3. How can I restore the vmicvss / VSS integration channel without rebuilding the guests?

Temporary mitigation: currently using crash-consistent backups only.

Windows for business | Windows Server | Storage high availability | Virtualization and Hyper-V
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  1. HLBui 11,090 Reputation points Independent Advisor
    2026-07-02T02:04:14.2633333+00:00

    Hi Emran Moradian •

    From what you’ve described, this looks less like a misconfiguration and more like a regression tied to the June 2026 cumulative updates on Windows Server 2025 build 26100. The fact that both guests fail identically, with vmicvss timing out at PID 0 despite healthy VMBus and VSS writers, strongly suggests the integration component itself is broken at the OS build level rather than anything you can fix inside the VM.

    At the moment, Microsoft hasn’t published a formal hotfix or KB that directly addresses this vmicvss startup failure, but there are two practical workarounds: (1) roll back the June CUs to confirm the regression disappears, or (2) switch to standard checkpoints or crash‑consistent backups until the next servicing release. If you’re running production workloads, I’d also recommend opening a support case with Microsoft CSS so they can track this as a potential servicing bug that helps push it into the queue for an out‑of‑band fix. Rebuilding the guests won’t help since the issue is tied to the integration service binaries shipped in build 26100. For now, your mitigation of crash‑consistent backups is the safest path until a patch lands

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