How severe is CVE-2023-21809?

High severity. CVSS v3 base score is 7.8 out of 10.

Vulnerability in Microsoft Defender Security Intelligence Updates

CVE-2023-21809

Microsoft Defender for Endpoint Security Feature Bypass Vulnerability

Published 2023-02-14 · last modified 2026-08-19.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.006 (46.7th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 46.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

Microsoft Defender Security Intelligence Updates
Microsoft Defender Security Intelligence Updates — versions 1.0.0

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21809 (vendor-advisory, Patch, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2023-21809?: CVE-2023-21809 is a high-severity vulnerability in Microsoft Defender Security Intelligence Updates. CVSS score: 7.8/10. Published 2023-02-14.
How severe is CVE-2023-21809?: High severity. CVSS v3 base score is 7.8 out of 10.