How severe is CVE-2021-40453?

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

Vulnerability in Microsoft Hevc Video Extensions

CVE-2021-40453

HEVC Video Extensions Remote Code Execution Vulnerability

Published 2021-12-15 · last modified 2026-06-17.

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: 0.022 (82.0th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 82nd percentile — 82.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.022 · newest: 0.022 · change: 0.000

Affected products

Microsoft Hevc Video Extensions
Microsoft Hevc Video Extensions

References

portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40453 (Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-40453?: CVE-2021-40453 is a high-severity vulnerability in Microsoft Hevc Video Extensions. CVSS score: 7.8/10. Published 2021-12-15.
How severe is CVE-2021-40453?: High severity. CVSS v3 base score is 7.8 out of 10.