---
id: "CVE-2026-20963"
kind: "vulnerability"
aliases: ["CVE-2026-20963"]
title: "microsoft sharepoint server: Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code\u2026"
severity: "critical"
cvss: 9.8
epss: null
exploited: true
status: "open"
category: "runtime"
products: [{"name": "Microsoft SharePoint", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft sharepoint server", "fixed": ["16.0.19127.20442"], "affected": "< 16.0.19127.20442", "ecosystem": "vendor"}, {"name": "microsoft sharepoint server", "fixed": [], "affected": "= 2016", "ecosystem": "vendor"}, {"name": "microsoft sharepoint server", "fixed": [], "affected": "= 2019", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "microsoft", "runtime", "self-hosted", "sharepoint"]
not_affected_if: ["sharepoint-online", "unknown"]
published_at: "2026-01-13T18:16:24+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T23:44:51+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-20963", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-20963", "first_seen_at": "2026-10-23T23:44:51+00:00"}]
---

# microsoft sharepoint server: Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code…

Microsoft SharePoint has a deserialization of untrusted data flaw that lets an unauthenticated attacker run code over the network. CISA lists it as actively exploited in the wild.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Microsoft SharePoint affected ? fixed ?
- vendor:microsoft sharepoint server affected < 16.0.19127.20442 fixed 16.0.19127.20442
- vendor:microsoft sharepoint server affected = 2016 fixed ?
- vendor:microsoft sharepoint server affected = 2019 fixed ?

## Fix

Apply the Microsoft mitigations or patch per vendor instructions; the sources do not name the fixed build.
If mitigations are unavailable, CISA says to discontinue use of the product.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-20963
- 2026-10-23T23:44:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-20963

## From the sources

Microsoft SharePoint contains a deserialization of untrusted data vulnerability that allows an unauthorized attacker to execute code over a network.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_