---
title: "CVE-2026-50522: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability "
url: https://erroneo.us/security/cve/CVE-2026-50522/
description: "CVE-2026-50522 (Microsoft SharePoint): Exploited in the wild (CISA KEV). Deserialization of untrusted data in Microsoft Office SharePoint allows an…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-14
date_modified: 2026-10-08
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-50522"
kev: true
cvss: 9.8
epss: 0.03042
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-50522: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability 

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Microsoft SharePoint. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-07-22, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-07-25 ; treat that as the outer limit, not the target.
- EPSS 3.0% , percentile 87: FIRST’s model estimates a 3.0% chance of exploitation activity in the next 30 days, higher than 87% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Act now. SharePoint: Four July-August 2026 Flaws Now Exploited — Any on-premises SharePoint farm not yet on the August 2026 builds is exposed to exploited bugs with public exploit code; patch, rotate machine keys and check for compromise now.

## What it is

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

## Affected products (CVE record)

- Microsoft Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001
- Microsoft Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175
- Microsoft Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434

## Severity

- microsoft CVSS 3.1: 9.8 `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`

## Exploitation

- CISA KEV: added 2026-07-22; federal due date 2026-07-25. Known ransomware use: Unknown.
- 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.
- CISA SSVC assessment: exploitation active , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 3.04% probability of exploitation activity in the next 30 days; percentile 87.

## Sources

- [Microsoft SharePoint Remote Code Execution Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50522)
- [CVE.org record CVE-2026-50522](https://www.cve.org/CVERecord?id=CVE-2026-50522)
- [NVD entry CVE-2026-50522](https://nvd.nist.gov/vuln/detail/CVE-2026-50522)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-50522)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)

---
Source page: https://erroneo.us/security/cve/CVE-2026-50522/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt