CVE-2026-96940

Microsoft Exchange Server Elevation of Privilege Vulnerability

CVE-2026-96940 is fixed in 4 products on 1 platform, first by KB5129958, released October 2, 2026. It is not reported as exploited, but the vendor rates exploitation more likely. Patch Radar priority: Urgent.

Urgent

CVSS

8.8

Important

Exploitation

More likely

Vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0275

86th percentile

<p>Weak authentication in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.</p>

Where it's fixed

Product	Fix	Released
Microsoft
Microsoft Exchange Server 2016 Cumulative Update 23	KB5129958	Oct 2, 2026
Microsoft Exchange Server 2019 Cumulative Update 14	KB5129957	Oct 2, 2026
Microsoft Exchange Server 2019 Cumulative Update 15	KB5129956	Oct 2, 2026
Microsoft Exchange Server Subscription Edition RTM	KB5129955	Oct 2, 2026

Details

Published
October 2, 2026
Weakness
Weak Authentication
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-96940

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