Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-50522 – Unauthenticated RCE via Deserialization – Microsoft SharePoint Server (Enterpris…

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-50522 is a critical deserialization vulnerability in Microsoft SharePoint Server, affecting Enterprise Server 2016, Server 2019, and the Subscription Edition. The flaw arises from insecure deserialization of untrusted data (CWE-502), enabling unauthorized remote attackers to execute arbitrary code over the network with no authentication and no user interaction required. It carries a CVSS v3.1 base score of 9.8 (Critical), representing a maximum-severity risk for any internet-facing SharePoint deployment.

Technical details

  • Root cause: Deserialization of untrusted data (CWE-502) within Microsoft Office SharePoint’s processing pipeline allows attacker-controlled serialized objects to be loaded and executed server-side.
  • Trigger conditions: No authentication is required (Privileges Required: NONE) and no user interaction is needed (UI: NONE), meaning the vulnerability is exploitable entirely by a remote, unauthenticated attacker.
  • Attack vector: Network-reachable with low attack complexity (AV:N/AC:L); any SharePoint instance accessible from the internet is within scope.
  • Impact: Full compromise across all three security dimensions — high Confidentiality, Integrity, and Availability impact (C:H/I:H/A:H) — consistent with arbitrary remote code execution on the underlying server.

Affected software

  • Microsoft SharePoint Enterprise Server 2016 (x64-based Systems) — versions prior to 16.0.5561.1001
  • Microsoft SharePoint Server 2019 (x64-based Systems) — versions prior to 16.0.10417.20175
  • Microsoft SharePoint Server Subscription Edition (x64-based Systems) — versions prior to 16.0.19725.20434

Severity

CVSS v3.1 Base Score: 9.8 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate — apply Microsoft’s security update:
    • SharePoint Enterprise Server 2016: upgrade to 16.0.5561.1001 or later
    • SharePoint Server 2019: upgrade to 16.0.10417.20175 or later
    • SharePoint Server Subscription Edition: upgrade to 16.0.19725.20434 or later
  • If patching cannot be applied immediately: Restrict network access to SharePoint instances at the perimeter, blocking unauthenticated inbound connections from the public internet. Prioritize exposure reduction for any SharePoint server directly reachable from outside the organization.
  • Monitor SharePoint server logs for anomalous deserialization activity or unexpected process execution.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge