Check Exchange vulnerability exposure in two separate ways: verify each server’s exact edition, build, security updates, and required actions against Microsoft’s release guidance, then assess whether the relevant services are reachable from networks that should not access them. A build check alone does not establish network exposure, and an externally reachable endpoint alone does not prove that a specific vulnerability is present.
1. Identify each server’s edition and installed build
Start with an inventory of the Exchange servers in scope. On each server, run Microsoft’s Exchange Health Checker and review its Exchange Information output, especially Build Number and Exchange IU or Security Hotfix Detected. Microsoft recommends Health Checker for verifying build information.
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The Exchange build reference also documents this PowerShell command for checking the installed ExSetup.exe file version:
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Do not treat this command as interchangeable with Get-ExchangeServer output. For example:
Get-ExchangeServer | Format-List Name,Edition,AdminDisplayVersion
That display reports the CU version, but it does not confirm which security update (SU) or hotfix (HU) is installed. Use Health Checker and the installed file version when validating update state.
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2. Match the exact build to the right Microsoft release information
Compare each server’s edition and exact build with Microsoft’s Exchange Server build numbers and release dates page. Use the section for that Exchange release; the table distinguishes cumulative updates (CUs), security updates, hotfixes, and other builds. A CU label by itself is not enough to establish that the server has a later SU or HU.
Check support status as well as the number. As of October 2026, Microsoft says Exchange Server 2016 and Exchange Server 2019 are out of support. Microsoft’s cited guidance says customers enrolled in the Extended Security Update (ESU) program are eligible for December 2025 and later security updates; customers outside ESU are directed to migrate to Exchange Server Subscription Edition. Confirm the applicable support and ESU details for your environment in Microsoft’s current guidance rather than assuming an old build remains covered.
3. Find missing updates and required manual actions
Run Health Checker across the Exchange environment to identify servers behind on CUs or SUs and to surface required manual actions. Microsoft recommends installing applicable security updates, then running Health Checker again: some updates can require additional actions after installation.
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Keep the Exchange host operating system updated too. Exchange application update status does not establish that the underlying Windows Server is current.
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If the Exchange Emergency Mitigation (EM) service is in use, check which mitigations have been applied to each server. Microsoft documents this command:
Get-ExchangeServer -Identity <ServerName> | Format-List Name,MitigationsApplied
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The EM service can apply measures such as URL rewrite rules or disabling a vulnerable service or app pool. Treat those measures as interim protection, not as proof that the vulnerability’s code fix is installed. Microsoft states: “Each mitigation is a temporary, interim fix until you can apply the Security Update that fixes the vulnerability.” Its update FAQ likewise calls mitigations temporary protection to use until the actual code fix is released. Apply the applicable security update and complete any required manual actions.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.5. Assess whether Exchange is reachable from outside the intended network
Patch state and network reachability answer different questions. To investigate exposure, arrange an authorized outside-in assessment of the relevant Exchange hostnames, IP addresses, and services from the network vantage points that matter—for example, the public internet if the concern is internet access. The Microsoft references cited here document local build, update, and configuration checks; they do not specify a complete external scanning procedure or name a scanner.
Interpret an externally visible endpoint narrowly: it shows reachability from the assessment’s vantage point, not by itself that a particular CVE is exploitable or that the server lacks its fix. Correlate a vulnerability finding with the Exchange edition and exact build, the Microsoft guidance for the relevant release, and any required configuration or manual actions.
Compare findings using the same criteria
When reviewing two servers or an assessment report, compare these factors separately:
Quick Recap
- Edition and exact build: Identify the Exchange release and installed file/build version.
- Applicable update and support status: Check the relevant CU, SU, or HU and whether the release is supported or covered by ESU.
- Follow-up protection: Verify required manual actions and any EM mitigations applied.
- Network reachability: Record what was reachable, from which authorized vantage point, and on which relevant hostnames, IP addresses, or services.
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