---
id: "CVE-2026-123390"
page: "https://infrastack.ai/live/CVE-2026-123390"
kind: "vulnerability"
aliases: ["CVE-2026-123390"]
title: "Microsoft SharePoint: untrusted data deserialization lets an authorized user run code"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "vendor"
products: [{"name": "SharePoint Server Subscription Edition", "fixed": ["16.0.20326.20136"], "affected": ">= 16.0.0, < 16.0.20326.20136", "ecosystem": "vendor"}]
ecosystems: []
tags: ["microsoft-office", "on-premises", "self-hosted", "sharepoint", "vendor"]
not_affected_if: ["managed-hosting", "sharepoint-online"]
published_at: "2026-11-10T19:20:42+00:00"
first_seen_at: "2026-11-10T19:25:12+00:00"
updated_at: "2026-11-10T21:30:08+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123390", "first_seen_at": "2026-11-10T19:25:12+00:00"}, {"source": "analyst", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123390", "first_seen_at": "2026-11-10T21:30:08+00:00", "cites": ["https://nvd.nist.gov/vuln/detail/CVE-2026-123390", "https://app.opencve.io/cve/CVE-2026-123390"]}]
exploit_sources: []
---

# Microsoft SharePoint: untrusted data deserialization lets an authorized user run code

Link for people: https://infrastack.ai/live/CVE-2026-123390 (this .md is for agents)

Microsoft SharePoint mishandles untrusted serialized data, so an attacker with a valid account can run code over the network. NVD rates it high (CVSS 8.8).

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

## Affected

- vendor:SharePoint Server Subscription Edition affected >= 16.0.0, < 16.0.20326.20136 fixed 16.0.20326.20136

## How to check

On SharePoint Server Subscription Edition, check the farm build (Central Administration > Upgrade and Migration > Check product and patch installation status, or Get-SPFarm | select BuildVersion). Builds below 16.0.20326.20136 are listed as affected in the CVE record. Also check SharePoint 2016/2019 against the MSRC entry; the CVE record lists only Subscription Edition.

## Fix

Install the November 2026 SharePoint Server Subscription Edition security update, build 16.0.20326.20136 or later (per the CVE record; confirm the KB on the MSRC entry).

## Timeline

- 2026-11-10T19:25:12+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123390
- 2026-11-10T21:30:08+00:00 analyst https://nvd.nist.gov/vuln/detail/CVE-2026-123390 — MSRC page is JS-only and unreadable here; NVD (CNA Microsoft data) and OpenCVE give SharePoint Server Subscription Edition < 16.0.20326.20136. Not verified against MSRC; no exploitation or PoC seen (not in KEV). Recheck MSRC for 2016/2019 and KB.

## Documents

- [describes] NVD CVE-2026-123390 https://nvd.nist.gov/vuln/detail/CVE-2026-123390
- [describes] OpenCVE CVE-2026-123390 (CNA affected versions) https://app.opencve.io/cve/CVE-2026-123390

## From the sources

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

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_