CVE-2026-70571

Microsoft Exchange Server Remote Code Execution Vulnerability

CVE-2026-70571 is fixed in 4 products on 1 platform, first by KB5128898, released October 13, 2026. It is not reported as exploited, but the vendor rates exploitation more likely. Patch Radar priority: Urgent.

Urgent

CVSS

8.1

Critical

Exploitation

More likely

Vendor assessment

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0139

72nd percentile

<p>Stack-based buffer overflow in Microsoft Exchange Server allows an unauthorized attacker to execute code 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
Stack-based Buffer Overflow
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70571

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