CVE-2026-21509
Microsoft Office Security Feature Bypass Vulnerability
- Published
- Jan 26, 2026
- Updated
- Jul 30, 2026
- Assigning CNA
- microsoft
- Evidence observed
- Jan 26, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HHigh · next 30 days
- Percentile
- 99.4%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
CISA Known Exploited
This CVE appears in the CISA Known Exploited Vulnerabilities catalog.
Summary
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Sources
12- detect_CVE-2026-21509Detection
YARA rule and python script to detect potential exploits for the CVE-2026-21509 vulnerability in MS Office
- CVE-2026-21509-PoCResearch
Educational PoC generating a harmless DOCX with dummy OLE artifacts to test EDR/AV visibility, ASR rules, and sandbox analysis for CVE-2026-21509. For isolated labs only.
Proof-of-concept exploit for Microsoft Office security feature bypass (CVE-2026-21509). Generates malicious DOCX files with embedded OLE objects to test security controls and validate patches.
Responsible use
Use vulnerability information only on systems you own or are authorized to test. Kitploit links to public research metadata and does not store exploit code or malicious payloads.