CVE-2025-64666
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedImproper input validation in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThis is an improper input validation vulnerability in Microsoft Exchange Server that allows an authorized attacker to elevate privileges over a network. The vulnerability stems from the server not properly validating input, which could be exploited by an authenticated user to gain higher-level access within the Exchange environment.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data= 2016= 2019< 15.02.2562.035CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Exchange Server versionRun Get-ExchangeServer | Select-Object Name, Edition, AdminDisplayVersion in Exchange Management Shell, or check the version via Control Panel > Programs and Features > Microsoft Exchange ServerAffected if Version matches Exchange Server 2016 or 2019, or is Subscription Edition below 15.02.2562.035
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Confirm Exchange build numberRun Get-ExchangeServer | Format-List to see the full build version, or use the Exchange Admin Center to view server version detailsAffected if Build number is below 15.02.2562.035 for Subscription Edition, or is a 2016/2019 release matching the affected version range
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Verify authentication is enabledCheck Exchange service configuration via Get-Service MSExchange* and ensure Exchange services are running; confirm the server accepts authenticated connections via ECP or EWSAffected if Exchange services are running and the server handles authenticated user requests, which is the typical default configuration
Your environment is affected if you run any Microsoft Exchange Server 2016, 2019, or Subscription Edition with a build version below 15.02.2562.035, as the privilege escalation via improper input validation can be exploited by any authenticated user.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped15.02.2562.035
Apply the Microsoft security update for this vulnerability to Exchange Server following Microsoft's published guidance; ensure proper testing of Exchange services and mail flow after patching.
Exchange Server 2016: Cumulative Update 23 or later; Exchange Server 2019: Cumulative Update 15 or later; Exchange Server Subscription Edition: Version 15.02.2562.035 or later
- Identify your current Exchange Server version by running Get-ExchangeServer | Format-List Name,Edition,AdminDisplayVersion in Exchange Management Shell
- For Exchange Server 2016, install Cumulative Update 23 or later (Cumulative Update 23 is build 15.01.2507.xxx)
- For Exchange Server 2019, install Cumulative Update 15 or later (Cumulative Update 15 is build 15.02.2698.xxx or higher)
- For Exchange Server Subscription Edition, ensure the version is 15.02.2562.035 or higher
- Download the appropriate Cumulative Update from the Microsoft Update Catalog or Volume Licensing Service Center
- Review the Cumulative Update release notes for any pre-installation requirements
- Backup your Exchange Server configuration and databases
- Install the Cumulative Update on your Exchange Servers, starting with the servers that do not have the Mailbox role (Edge Transport servers first, then Mailbox servers)
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-64666 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-64666 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data