---
id: "CVE-2026-58644"
kind: "vulnerability"
aliases: ["CVE-2026-58644"]
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: "vendor"
products: [{"name": "Microsoft SharePoint", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft sharepoint server", "fixed": ["16.0.19725.20434"], "affected": "< 16.0.19725.20434", "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", "self-hosted", "sharepoint", "vendor"]
not_affected_if: ["managed-hosting", "sharepoint-online"]
published_at: "2026-07-14T17:17:14+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-2026-58644", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-58644", "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 < 16.0.19725.20434 fixed 16.0.19725.20434
- vendor:microsoft sharepoint server affected = 2016 fixed ?
- vendor:microsoft sharepoint server affected = 2019 fixed ?

## Fix

Apply the mitigations and patch from Microsoft's advisory for CVE-2026-58644 as directed by CISA BOD 26-04; if no mitigation exists, discontinue use of the affected SharePoint product.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-58644
- 2026-10-23T23:44:51+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-58644

## 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 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.

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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_