VulnerabilityAnalyzed

CVE-2026-20963

Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

KEVCRITICAL 9.8EPSS 32.6%

Does this matter?

Known to be exploited in the wild (CISA KEV, CISA remediation deadline 21 March 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.

Description

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

CVSS 3.1: 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 32.61% probability · 98th percentile
CISA KEV: Listed 18 March 2026 · due 21 March 2026
Weakness: CWE-502
Affected: microsoft/sharepoint server
Source: secure@microsoft.com

CISA notes

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20963 ; https://nvd.nist.gov/vuln/detail/CVE-2026-20963

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20963Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20963US Government Resource

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.