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CVE-2021-34520: Microsoft SharePoint Server Remote Code Execution Vulnerability

• Severity: medium (CVSS 6.5 v2.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 4.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-07-14 · updated 2026-08-10
• Weakness: CWE-502

Description

Microsoft SharePoint Server Remote Code Execution Vulnerability

Affected products

• Microsoft SharePoint Foundation 2013 Service Pack 1: 2013-sp1
• Microsoft SharePoint Server: 2016, 2019
• Microsoft Sharepoint Enterprise Server 2016: from 16.0.0 before 16.0.5188.1000 — fixed in 16.0.5188.1000
• Microsoft SharePoint Foundation 2013 Service Pack 1: from 15.0.0 before 15.0.5363.1000 — fixed in 15.0.5363.1000
• Microsoft SharePoint Server: from 16.0.0 before 16.0.10376.20001 — fixed in 16.0.10376.20001

How to fix

Upgrade to a fixed version: Microsoft Sharepoint Enterprise Server 2016 16.0.5188.1000; Microsoft SharePoint Foundation 2013 Service Pack 1 15.0.5363.1000; Microsoft SharePoint Server 16.0.10376.20001. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34520
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34520
• https://www.zerodayinitiative.com/advisories/ZDI-21-828/

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