CVE-2026-87696

Microsoft Exchange Server Elevation of Privilege Vulnerability

CVE-2026-87696 is fixed in 4 products on 1 platform, first by KB5128898, released October 13, 2026. It is not reported as exploited. Patch Radar priority: High.

High

CVSS

7.5

Important

Exploitation

None reported

Exploitation Less Likely

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0042

36th percentile

<p>Improper verification of cryptographic signature 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	KB5128898	Oct 13, 2026
Microsoft Exchange Server 2019 Cumulative Update 14	KB5128897	Oct 13, 2026
Microsoft Exchange Server 2019 Cumulative Update 15	KB5128896	Oct 13, 2026
Microsoft Exchange Server Subscription Edition RTM	KB5128895	Oct 13, 2026

Details

Published
October 13, 2026
Weakness
Improper Verification of Cryptographic Signature
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-87696

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