CVE-2026-21509 — AI Deep Analysis Summary

🚨 **Essence**: Microsoft Office has a **Security Feature Bypass** vulnerability. <br>💥 **Consequences**: Attackers can **bypass security controls** relying on untrusted input.…

🔍 **Root Cause**: **CWE-807** (Security Decision Reliance on Untrusted Input).…

🏢 **Affected Vendor**: **Microsoft**. <br>💻 **Product**: **Microsoft 365 Apps for Enterprise** (including Word, Excel, PowerPoint, etc.). <br>📅 **Published**: Jan 26, 2026.

🕵️ **Attacker Action**: Local attackers can **bypass security features**.…

📉 **Threshold**: **LOW**. <br>🔑 **Auth**: **None required** (PR:N). <br>🖱️ **User Interaction**: **Required** (UI:R) - victim must open the file. <br>⚡ **Complexity**: **Low** (AC:L). Easy to exploit if the user clicks.

🔥 **Public Exploits**: **YES**. <br>📂 **PoCs Available**: Multiple GitHub repos exist (e.g., `Ashwesker`, `gavz`, `SimoesCTT`).…

🔎 **Self-Check**: <br>1. Check if running **Microsoft 365 Apps for Enterprise**. <br>2. Scan for **OLE/COM artifacts** in DOCX files. <br>3.…

🛡️ **Official Fix**: **YES**. <br>📥 **Patch**: Microsoft released an **emergency patch** via the Update Guide. <br>🔗 **Reference**: [MSRC Advisory](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509).…

🚧 **No Patch Workaround**: <br>1. **Disable OLE/COM** execution where possible. <br>2. **Block NFSv4.1** kernel driver (`nfssvr.sys`) if not needed. <br>3.…

🚨 **Urgency**: **CRITICAL / IMMEDIATE ACTION**. <br>📉 **CVSS**: High impact (C:H, I:H, A:H). <br>⚡ **Exploitability**: Low complexity + No auth needed.…