CVE-2026-45659

Microsoft SharePoint Remote Code Execution Vulnerability

CVE-2026-45659 is fixed in 3 products on 1 platform, first by KB5002868, released May 12, 2026. It is being exploited: CISA added it to the Known Exploited Vulnerabilities catalog on July 1, 2026, with known ransomware use. Patch Radar priority: Patch now.

Patch nowCISA KEVKnown ransomware use

CVSS

8.8

Important

Exploitation

Exploited

Listed by CISA

CISA KEV

Jul 1, 2026

Federal due date Jul 4, 2026. Known ransomware use

EPSS

0.8024

99th percentile

<p>Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.</p>

Where it's fixed

Product	Fix	Released
Microsoft
Microsoft SharePoint Enterprise Server 2016	KB5002868	May 12, 2026
Microsoft SharePoint Server 2019	KB5002870	May 12, 2026
Microsoft SharePoint Server Subscription Edition	KB5002863	May 12, 2026

Details

Published
May 26, 2026
Weakness
Deserialization of Untrusted Data
CISA required action
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45659

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