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CVE-2026-45659

Microsoft SharePoint Server Deserialization of Untrusted Data Vulnerability

Microsoft SharePoint ServerApplications & CMS
Open in ThreatlineRecord JSON
CVSS
8.8High
ExploitationExploited in the wildAdded to KEV 1 Jul 2026. Known ransomware useCISA KEV
Exploit odds (EPSS)2.70%Chance of exploitation activity in the next 30 days, higher than 85% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in16.0.5552.1002Also 16.0.10417.20128, 16.0.19725.20280CVE List
Federal deadline4 Jul 2026Remediation due date for US federal agenciesCISA KEV
CISA required actionApply 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. CISA KEV
Patching is not enoughCISA requires federal agencies to look for signs of compromise on affected systems, not only patch (forensic triage under BOD 26-04). Treat exposed systems as possibly compromised. CISA guidance

What fixes it

  • 16.0.5552.1002Microsoft SharePoint Enterprise Server 2016CVE List
  • 16.0.10417.20128Microsoft SharePoint Server 2019CVE List
  • 16.0.19725.20280Microsoft SharePoint Server Subscription EditionCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Timeline

  1. 22 May 2026, 22:04 UTCPublishedCVE List
  2. 1 Jul 2026Added to CISA KEVCISA KEV

Description

Microsoft SharePoint Server contains a deserialization of untrusted data vulnerability which allows an authorized attacker to execute code over a network.

Text from CVE List

Affected versions 3

  • Microsoft SharePoint Enterprise Server 2016affected: 16.0.0 before 16.0.5552.1002CVE List
  • Microsoft SharePoint Server 2019affected: 16.0.0 before 16.0.10417.20128CVE List
  • Microsoft SharePoint Server Subscription Editionaffected: 16.0.0 before 16.0.19725.20280CVE List

References 3