# CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability

CVE-2026-21509 is fixed in 2 products on 1 platform, first by KB5002713, released January 26, 2026. It is being exploited: CISA added it to the Known Exploited Vulnerabilities catalog on January 26, 2026. Patch Radar priority: Patch now.

- Web page: https://patchblox.com/security/cve/CVE-2026-21509
- Priority: Patch now
- CVSS: 7.8 (Important)
- EPSS: 0.7080
- CISA KEV: listed Jan 26, 2026, federal due date Feb 16, 2026
- Exploited (vendor report): yes
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Detected
- Published: Jan 26, 2026
- Weakness: Reliance on Untrusted Inputs in a Security Decision
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509

## Description

<p>Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft Office 2016 (32-bit edition) |  | [KB5002713](https://patchblox.com/security/data/fix/microsoft/kb5002713.md) | Jan 26, 2026 |
| Microsoft | Microsoft Office 2016 (64-bit edition) |  | [KB5002713](https://patchblox.com/security/data/fix/microsoft/kb5002713.md) | Jan 26, 2026 |

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Data as of 2026-11-09T13:31:49Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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