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CVE-2021-26420: Microsoft SharePoint Server Remote Code Execution Vulnerability

• Severity: medium (CVSS 6.5 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-06-08 · updated 2026-06-17

Description

Microsoft SharePoint Server Remote Code Execution Vulnerability

Affected products

• Microsoft SharePoint Server: 2016
• Microsoft SharePoint Foundation 2013 Service Pack 1: 2013-sp1
• Microsoft SharePoint Server: 2019
• Microsoft Sharepoint Enterprise Server 2016: from 16.0.0 before 16.0.5173.1000 — fixed in 16.0.5173.1000
• Microsoft SharePoint Foundation 2013 Service Pack 1: from 15.0.0 before 15.0.5353.1000 — fixed in 15.0.5353.1000
• Microsoft SharePoint Server: from 16.0.0 before 16.0.10375.20000 — fixed in 16.0.10375.20000

How to fix

Upgrade to a fixed version: Microsoft Sharepoint Enterprise Server 2016 16.0.5173.1000; Microsoft SharePoint Foundation 2013 Service Pack 1 15.0.5353.1000; Microsoft SharePoint Server 16.0.10375.20000. Check the vendor advisory for mitigations.

References

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26420
• https://www.zerodayinitiative.com/advisories/ZDI-21-755/
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26420
• https://www.zerodayinitiative.com/advisories/ZDI-21-755/

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