CVE-2026-20963

Description

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

Overview

State: PUBLISHED
Assigner (CNA): microsoft
CVSS severity: CRITICAL
CVSS score: 9.8 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Effective score: 9.8 / 10 CRITICAL source: CNA overview
MSRC score: 9.8 / 10 CRITICAL MS rating: Important · Remote Code Execution
CWE(s): CWE-502
Reserved: 2025-12-04
Published: 2026-01-13 08:00 UTC
Last updated: 2026-03-17 07:00 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/20xxx/CVE-2026-20963.json
Linked Threat: CVE-2026-20963 — Microsoft SharePoint: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

CISA Known Exploited Vulnerabilities CISA KEV

CISA has confirmed in-the-wild exploitation of this CVE. Federal agencies must remediate by the due date below; private orgs should treat it as priority-1.

Vulnerability name: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability
Vendor / project: Microsoft
Product: SharePoint
Date added to KEV: 2026-03-18
Remediation due: 2026-03-21
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.
Ransomware campaign use: Unknown
CISA notes: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20963 ; https://nvd.nist.gov/vuln/detail/CVE-2026-20963
CISA listing: www.cisa.gov/known-exploited-vulnerabilities-catalog

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-01-13 18:16:24 UTC
NVD last modified: 2026-04-01 16:01:22 UTC
NVD CVSS v3.1: 9.8 / 10 CRITICAL source: secure@microsoft.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitability subscore: 3.9 / 10
Impact subscore: 5.9 / 10
EPSS score: 0.0562 (probability of exploitation in next 30 days)
EPSS percentile: 90.44% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-2114
Assigner: microsoft
Published: Jan 13, 2026, 5:56:49 PM
Updated: Apr 2, 2026, 3:55:34 AM
EUVD base score (CVSS 3.1): 9.8 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
EUVD-reported EPSS: 5.2900
Vendors: Microsoft
Products: Microsoft SharePoint Server 2019 (16.0.0 <16.0.10417.20083)

Microsoft SharePoint Server Subscription Edition (16.0.0 <16.0.19127.20442)

Microsoft SharePoint Enterprise Server 2016 (16.0.0 <16.0.5535.1001)
Aliases: GHSA-5vr8-9cf6-r7px

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

EUVD references (1)

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20963

Microsoft Security Response Center MSRC

Microsoft's vendor-authoritative record from the Security Update Guide — its own CVSS score, impact, severity rating, exploit assessment, and KB-article fixes. Refreshed 2026-07-31 03:00 UTC (source: CVRF).

MS severity: Important
Impact: Remote Code Execution
MS CVSS base score: 9.8 / 10 (temporal 8.5)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Exploit assessment: Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation Less Likely
Release: 2026-Jan

Microsoft remediations / KB articles (6)

5002828 — Vendor Fix / Security Update (fixed build 16.0.5535.1001)
https://support.microsoft.com/help/5002828 — None Available / 5002828
5002825 — Vendor Fix / Security Update (fixed build 16.0.10417.20083)
https://support.microsoft.com/help/5002825 — None Available / 5002825
5002822 — Vendor Fix / Security Update (fixed build 16.0.19127.20442)
https://support.microsoft.com/help/5002822 — None Available / 5002822

Microsoft FAQ (1)

How could an attacker exploit this vulnerability?

In a network-based attack, an unauthenticated attacker could write arbitrary code to inject and execute code remotely on the SharePoint Server.

Affected products (3)

Vendor	Product	Versions	Platforms
Microsoft	Microsoft SharePoint Enterprise Server 2016	`16.0.0` (affected)	x64-based Systems
Microsoft	Microsoft SharePoint Server 2019	`16.0.0` (affected)	x64-based Systems
Microsoft	Microsoft SharePoint Server Subscription Edition	`16.0.0` (affected)	x64-based Systems

Affected products — CPE 2.3 (3) NVD

NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.

cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*
cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*
cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*

Vendor references (1)

References embedded in the original CVE record by the assigning CNA.

Microsoft SharePoint Remote Code Execution Vulnerability vendor-advisorypatch

Web references (11)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

5002822 msrc
5002828 msrc
5002825 msrc
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20963 rapid7:msrc.microsoft.com
https://support.microsoft.com/help/5002822 rapid7:support.microsoft.com
http://cwe.mitre.org/data/definitions/502.html rapid7:cwe.mitre.org
https://support.microsoft.com/help/5002828 rapid7:support.microsoft.com
https://www.cve.org/CVERecord?id=CVE-2026-20963 rapid7:www.cve.org
https://support.microsoft.com/help/5002825 rapid7:support.microsoft.com
https://attackerkb.com/topics/CVE-2026-20963 rapid7:attackerkb.com
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-2114 rapid7:euvd.enisa.europa.eu

NVD-tagged references (2)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20963 secure@microsoft.com Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20963 134c704f-9b21-4f2e-91b3-4a467353bcc0 US Government Resource

Indicators (2)

IOCs linked to the auto-promoted Threat row.

Type	Value	VirusTotal	Attached
cwe	`CWE-502`	no local data	2026-05-14 02:58 UTC
cve	`CVE-2026-20963`	no local data	2026-05-14 02:58 UTC

Remediations (1)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

CISA Required Action

CISA KEV

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Due date: 2026-03-21 Known ransomware campaign use: Unknown

2026-05-14 01:13 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-20963.json.

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