Microsoft Security Response CenterCVE-2026-45503

Microsoft Exchange Server Information Disclosure Vulnerability

Improper authorization in Microsoft Exchange Server allows an authorized attacker to disclose information over a network.

Read the vendor bulletin Get alerts for Microsoft Exchange Server 2016 Cumulative Update

8.1CVSS out of 10High severity

Scope

What the vendor says is affected

Microsoft Exchange Server 2016 Cumulative Update 23
Microsoft Exchange Server Subscription Edition RTM
Microsoft Exchange Server 2019 Cumulative Update 15
Microsoft Exchange Server 2019 Cumulative Update 14

Versions the vendor lists as fixed

15.01.2507.071
15.02.2562.045
15.02.1748.048
15.02.1544.043

Next step

What the vendor recommends

Install KB5103215. Install KB5103212. Install KB5103213. Install KB5103214.

Review the complete instructions on the vendor's site

Timeline

When this advisory changed

Jun 9, 2026 at 7:00 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Sep 28, 2026 at 11:20 AM UTC
Added to SecurityAlert
We collected the advisory from the official source.

Vulnerabilities

CVEs named in this advisory

CVE-2026-45503View CVSS, KEV, EPSS, and threat context

Source

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Vendor: Microsoft Security Response Center
Advisory ID: CVE-2026-45503
Last source check: Sep 28, 2026 at 11:20 AM UTC

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Your environment

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Test the update or mitigation through your normal change process.

Watch Microsoft Exchange Server 2016 Cumulative Update

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What the vendor says is affected

Versions the vendor lists as fixed

What the vendor recommends

When this advisory changed

CVEs named in this advisory

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