CVE-2026-55040 PoC: Microsoft SharePoint JWT authentication bypass

CVE

CVE-2026-55040

Vendor

Microsoft

Product

SharePoint Server

Affected versions

SharePoint 2016 < 16.0.5561.1001; 2019 < 16.0.10417.20175; Subscription Edition < 16.0.19725.20434

CVSS

9.1

Published

2026-07-28 08:46

Collected

2026-08-13 23:17

---
id: 6538
title: "CVE-2026-55040 PoC: Microsoft SharePoint JWT authentication bypass"
cve: CVE-2026-55040
cvss: 9.1
vendor: "Microsoft"
product: "SharePoint Server"
affected_versions: "SharePoint 2016 < 16.0.5561.1001; 2019 < 16.0.10417.20175; Subscription Edition < 16.0.19725.20434"
source_domain: github.com
source_url: "https://github.com/l0ggg/CVE-2026-55040"
published_at: "2026-07-28T08:46:15Z"
tags: ["public-poc", "authentication-bypass", "microsoft", "pre-auth", "sharepoint", "jwt", "exploit", "poc", "cve-2026-55040"]
phying_url: "https://phying.com/item/6538"
lang: en
---

# CVE-2026-55040 PoC: Microsoft SharePoint JWT authentication bypass

## Summary

A PoC for CVE-2026-55040: exploit code that constructs an authentication header for any valid account, demonstrating a JWT authentication bypass in Microsoft SharePoint.

## Why it matters

The public PoC can generate a forged authentication token for a specified account, substantially lowering the barrier to validation and reproduction. Apply Microsoft security updates immediately and test only in isolated, authorized environments.

## Intelligence Metadata

- **Sources:** github.com
- **CVE:** CVE-2026-55040
- **CVSS:** 9.1
- **Vendor:** Microsoft
- **Product:** SharePoint Server
- **Affected versions:** SharePoint 2016 < 16.0.5561.1001; 2019 < 16.0.10417.20175; Subscription Edition < 16.0.19725.20434
- **Published:** 2026-07-28T08:46:15Z
- **Original:** https://github.com/l0ggg/CVE-2026-55040
- **Phying News:** https://phying.com/item/6538