Why Are October Updates Failing with Error 0x80073701 and How Can You Fix This Nightmare?

Can You Effortlessly Resolve Windows Server Error 0x80073701 Without a Clean Install?

Reports confirm that the cumulative updates released in October and November 2025 (specifically KB5066586 and KB5068791) are aborting installation with the error code 0x80073701. Standard remediation tools like SFC and DISM often return clean results, leaving IT professionals with no clear path forward.

This guide breaks down the root cause—specifically the ERROR_SXS_ASSEMBLY_MISSING flag—and provides a proven PowerShell solution to resolve the registry corruption without requiring a full OS reinstallation.

The Diagnosis: Identifying the “Missing Assembly” Issue

When an update fails with 0x80073701, it typically indicates that the Windows Component Store is inconsistent. While standard tools check for file corruption, this specific error often points to registry logic corruption.

If you examine your CBS.log file (located at C:\Windows\Logs\CBS\CBS.log), you will likely see an entry similar to this:

Error STATUS_SXS_ASSEMBLY_MISSING originated in function CCSDirectTransaction::LockComponent...

What this actually means: The Windows Installer (TrustedInstaller) is attempting to pin a specific component for the update, but the registry tells it the component is missing or in an invalid state.

The Root Cause: “Staged” Packages

The underlying issue is often traced back to unexpected system interruptions (such as a crash or power loss) during a previous maintenance window. When this happens, update packages can get stuck in a “limbo” state within the registry.

These corrupted packages are often marked with a CurrentState hex value of:

• 0x40
• 0x50

These values indicate the package is “Staged”—files are present on the disk, but the system hasn’t fully committed them. Consequently, future updates fail because they cannot build upon these partially installed components.

The Solution: A PowerShell Registry Fix

Microsoft support may suggest an in-place upgrade or a full reinstall, which leads to significant downtime. However, a targeted PowerShell script can unblock these updates by marking the corrupted packages as “Absent,” forcing Windows to re-evaluate them correctly.

Critical Warning: This solution involves modifying the Windows Registry. Always create a full server backup or a snapshot of your Virtual Machine before running these commands.

Step 1: Verify Corrupted Packages

Run the following command in an elevated PowerShell (Administrator) window to identify if you have packages stuck in the 0x64 or related error states:

Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Packages\*" | Where-Object {$_.Currentstate -eq "64"} | Select-Object PSchildName

Step 2: The Remediation Script

If the log analysis confirms 0x80073701 or 0x800f0831, use the following script. This script scans the Component Based Servicing (CBS) registry keys for packages stuck in state 0x40 or 0x50 and resets them to 0 (Absent).

Copy and paste this into an administrative PowerShell console:

$name = 'CurrentState'
# Get all packages from the CBS registry key
$check = (Get-ChildItem -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Packages' -Recurse).Name

foreach ($check1 in $check) {
# Format the path for PowerShell access
$check2 = $check1.Replace("HKEY_LOCAL_MACHINE", "HKLM:")

# Check if the CurrentState is 0x40 or 0x50 (Staged/Corrupted)
$prop = Get-ItemProperty -Path $check2 -ErrorAction SilentlyContinue

if ($prop.$name -eq 0x50 -or $prop.$name -eq 0x40) {
# Output the name of the corrupted package
Write-Host "Fixing Corrupted Package: " $prop.PSChildName

# Reset the state to 0 (Absent)
Set-ItemProperty -Path $check2 -Name $name -Value 0
}
}
Write-Host "Scan and repair complete. Please reboot."

Step 4: Finalizing the Repair

Once the script has finished running:

1. Reboot the Windows Server immediately.
2. Navigate to Settings > Update & Security.
3. Click Check for Updates.

The system should now re-detect the missing components and successfully install the cumulative updates that were previously failing.