Microsoft Exchange Server Elevation of Privilege Vulnerability

Weak authorization in Microsoft Exchange Server allows an authenticated attacker to elevate privileges over a network.

Read the vendor bulletin Get alerts for Microsoft Exchange Server 2019 Cumulative Update

8.8CVSS out of 10High severity

Scope

What the vendor says is affected

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

Versions the vendor lists as fixed

15.02.1544.048
15.01.2507.075
15.02.2562.053
15.02.1748.053

Next step

What the vendor recommends

Install KB5129957. Install KB5129958. Install KB5129955. Install KB5129956.

Review the complete instructions on the vendor's site

Timeline

When this advisory changed

Oct 2, 2026 at 7:00 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Oct 3, 2026 at 12:50 AM UTC
Added to SecurityAlert
We collected the advisory from the official source.
Oct 3, 2026 at 6:55 AM UTC
Confirmed at the source
Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-96940View CVSS, KEV, EPSS, and threat context

Source

Start with the vendor's bulletin

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Vendor: Microsoft Security Response Center
Advisory ID: CVE-2026-96940
Last source check: Oct 3, 2026 at 1:00 PM 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 2019 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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