CVE-2026-45503
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 authorization in Microsoft Exchange Server allows an authorized attacker to disclose information over a network.
In the news
Third-party coverage- Microsoft June 2026 Patch Tuesday fixes 6 zero-days, 200 flaws
- Microsoft CVE Summary - Bleeping Computer
Surfaced from public web coverage — external links open in a new tab.
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 authorization vulnerability in Microsoft Exchange Server where an authenticated attacker can bypass normal authorization checks to disclose sensitive information over the network. The attacker already has valid credentials but exploits the authorization flaw to access data outside their intended permissions.
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< 15.02.2562.043CVSS 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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
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.
-
Identify Exchange Server versionRun Get-ExchangeServer | Format-List Name, Edition, AdminDisplayVersion or check registry key HKLM\SOFTWARE\Microsoft\ExchangeServer\v15\SetupVersionAffected if Version matches 2016, 2019, or Subscription Edition below 15.02.2562.043
-
Verify EWS or relevant web service endpoints are enabledCheck IIS site configuration for /EWS/ virtual directory and ensure Exchange Web Services are accessible via Get-WebServicesVirtualDirectoryAffected if EWS virtual directories exist and are accessible without additional auth restrictions
-
Review Exchange authentication configurationRun Get-WebServicesVirtualDirectory | Select-Object *Auth* to check authentication methods and externalURL settingsAffected if EWS uses forms-based or basic auth without strict token validation configured
-
Inspect IIS request filtering and URL authorizationCheck web.config in Exchange front-end sites and IIS URL Authorization module for custom deny rulesAffected if No restrictive authorization rules are in place for EWS paths
-
Search Exchange logs for anomalous EWS access patternsReview IIS logs in C:\inetpub\logs\LogFiles and EWS tracing logs for unusual GetItem or FindFolder requests with valid but low-privilege accountsAffected if Logs show access to folders or items outside the user's mailbox scope
Your environment is affected if you run Exchange 2016, 2019, or Subscription Edition below 15.02.2562.043 and EWS endpoints are accessible to authenticated users.
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.
From vendor data15.02.2562.043
Apply Microsoft Exchange Server security updates as soon as possible and review user/role permissions to ensure least-privilege access controls are enforced.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-45503 — 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-2026-45503 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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