IRONSMITHINTEL
CRITICALCVSS9.8
|CVE-2023-21554|Auth: none|Reboot: required|Manual only

KB5025230: Windows Server 2022 Security Update (April 2023)

A single crafted packet to TCP port 1801 gives an attacker SYSTEM-level code execution on any Windows Server running MSMQ.

Published Apr 11, 2023 · Updated May 21, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

An attacker who can reach TCP 1801 on a Windows Server with MSMQ installed can send a single crafted packet and execute code as SYSTEM. No authentication, no user interaction. MSMQ is widely installed for legacy ERP, financial, and integration workloads, and is frequently left exposed inside corporate networks — and sometimes on the internet.

How the attack works

Microsoft Message Queuing (MSMQ) is a Windows messaging service used by line-of-business applications for asynchronous communication. When installed, MSMQ listens on TCP 1801. Multiple input-validation bugs in MSMQ's parser let an attacker increment internal pointers past the bounds of the message buffer, producing out-of-bounds writes and a use-after-free condition. The result is unauthenticated SYSTEM-level code execution.

Am I affected?Quick check

Probably yes if any of these apply:

●Any Windows Server with the MSMQ feature installed
●Frequently includes Exchange (legacy), SCCM, and many third-party LOB application servers

Affected OS versions

Windows Server 2022
Real-world incidentsWhat we've seen

Researchers at Check Point scanned the internet at disclosure and found roughly 360,000 hosts exposing MSMQ on port 1801. Any of those exposed hosts could be compromised by a single packet, with no authentication. Inside corporate networks the exposure is wider still — MSMQ is installed by SCCM, Exchange (historically), and many third-party LOB applications, often without administrators realising it.

How to patch

Manual download

For air-gapped servers or out-of-band deployment. Microsoft Update Catalog returns every OS-version variant of this update.

↗ Microsoft Update CatalogKB5025230

Manual remediation steps

Check whether MSMQ is installed and exposed

MSMQ is sometimes installed by other software without administrators realising it. Check explicitly:

Get-WindowsFeature -Name MSMQ* | Where-Object Installed
Get-NetTCPConnection -LocalPort 1801 -State Listen -ErrorAction SilentlyContinue

If MSMQ is not needed, removing the feature is the strongest mitigation — patch is required regardless if the feature remains.

Prerequisites

    1
    Local administrator on the target server
    1
    Maintenance window with reboot capacity
    1
    Current backup or snapshot you can roll back to
    1
    Network path to Windows Update / WSUS / Microsoft Update Catalog

Estimated time

20–40 minutes per server (download + install + reboot)

Reboot required

Yes — install the cumulative update and reboot the server before the fix is active.

Steps

1. Confirm the server is missing the patch

Get-HotFix -Id KB5025230 -ErrorAction SilentlyContinue

2. Install the update — pick one channel

Windows Update / WSUS (preferred):

UsoClient ScanInstallWait
# (or use your standard WSUS / SCCM / Intune deployment for KB5025230)

Manual download (offline / air-gapped):

1
Open Microsoft Update Catalog: https://catalog.update.microsoft.com/Search.aspx?q=KB5025230
2
Download the MSU for Windows Server 2022 that matches your architecture (x64).
3
Copy the .msu file to the server and run as Administrator.

3. Reboot

Restart-Computer -Force

Verification

Get-HotFix -Id KB5025230
[System.Environment]::OSVersion.Version

If Get-HotFix returns nothing for KB5025230, the install did not take — re-run from a different channel.

Rollback

wusa.exe /uninstall /kb:5025230 /quiet /norestart
# Reboot after uninstall

Removing a cumulative update also removes every fix it delivered — prefer rolling forward.

Notes

    1
    This entry covers Windows Server 2022 specifically (KB5025230). Other Windows Server versions have their own KB for CVE-2023-21554.
    1
    Reference advisories: MSRC https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21554 and NVD https://nvd.nist.gov/vuln/detail/CVE-2023-21554.
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2023-21554↗ MSRC Advisory↗ NVD↗ KBKB5025230