CVE-2026-21509— Microsoft Office Security Feature Bypass Vulnerability
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I. Basic Information for CVE-2026-21509
Vulnerability Information
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Vulnerability Title
Microsoft Office Security Feature Bypass Vulnerability
Source: NVD (National Vulnerability Database)
Vulnerability Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
在安全决策中依赖未经信任的输入
Source: NVD (National Vulnerability Database)
Vulnerability Title
Microsoft Office 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Microsoft Office是美国微软（Microsoft）公司的一款办公软件套件产品。该产品常用组件包括Word、Excel、Access、Powerpoint、FrontPage等。 Microsoft Office存在安全漏洞，该漏洞源于安全决策依赖不可信输入，可能导致本地攻击者绕过安全功能。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Shenlong Deep Dive — AI Deep Analysis
10-question deep dive: root cause, exploitation, mitigation, urgency. Read summary free, full version requires login.
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 ~ https://aka.ms/OfficeSecurityReleases | - | |
| Microsoft | Microsoft Office 2016 | 16.0.0 ~ 16.0.5539.1001 | - | |
| Microsoft | Microsoft Office 2019 | 19.0.0 ~ 16.0.10417.20095 | - | |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 ~ https://aka.ms/OfficeSecurityReleases | - | |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 ~ https://aka.ms/OfficeSecurityReleases | - |
II. Public POCs for CVE-2026-21509
| # | POC Description | Source Link | Shenlong Link |
|---|---|---|---|
| 1 | CVE-2026-21509 | https://github.com/kimstars/Ashwesker-CVE-2026-21509 | POC Details |
| 2 | Educational PoC for CVE‑2026‑21509 (Microsoft Office security feature bypass). Generates a harmless DOCX with dummy OLE artifacts to study EDR/AV visibility. Not an exploit. For isolated labs only; see README for 7‑Zip inspection steps and mitigation references. | https://github.com/gavz/CVE-2026-21509-PoC | POC Details |
| 3 | Powershell script with Detection and Remediation for CVE-2026-21509 | https://github.com/ksk-itdk/KSK-ITDK-CVE-2026-21509-Mitigation | POC Details |
| 4 | New Physics Disclosure This repository contains a full weaponized exploit for **CVE-2026-21509**, targeting the Windows Network File System (NFSv4.1) kernel-mode driver (`nfssvr.sys`). | https://github.com/SimoesCTT/CTT-NFS-Vortex-RCE | POC Details |
| 5 | Microsoft just released emergency patches for CVE-2026-21509, a zero-day in the Office Suite that bypasses OLE/COM mitigations when a user simply opens a file. They think their "Service-side change" for Office 2021+ is a solid wall. | https://github.com/SimoesCTT/SCTT-2026-33-0007-The-OLE-Vortex-Laminar-Bypass- | POC Details |
| 6 | CVE-2026-21509 is a critical bypass in the Microsoft Office OLE (Object Linking and Embedding) validation engine. While standard "laminar" exploits attempt to manipulate static COM objects, this repository utilizes Theorem 4.2 to achieve a speculative race-condition bypass of the Object Definition Rule (ODR). | https://github.com/SimoesCTT/CTT-MICROSOFT-OFFICE-OLE-MANIFOLD-BYPASS-CVE-2026-21509 | POC Details |
| 7 | YARA rule and python script to detect potential exploits for the CVE-2026-21509 vulnerability in MS Office | https://github.com/decalage2/detect_CVE-2026-21509 | POC Details |
| 8 | None | https://github.com/kaizensecurity/CVE-2026-21509 | POC Details |
| 9 | CVE-2026-21509 Mitigation | https://github.com/planetoid/cve-2026-21509-mitigation | POC Details |
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IV. Related Vulnerabilities
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V. Comments for CVE-2026-21509
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