What is CVE-2021-28465?

CVE-2021-28465 is a high-severity vulnerability in Microsoft Web Media Extensions, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2021-05-11.

How severe is CVE-2021-28465?

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

Buffer overflow in Microsoft Web Media Extensions

CVE-2021-28465

Web Media Extensions Remote Code Execution Vulnerability

Vulnerability class: Buffer Overflow

Published 2021-05-11 · 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: 0.037 (89.6th percentile), scored 2026-10-24.

Low probability of exploitation in the next 30 days, but still tracked. 90th percentile — 89.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.037 · newest: 0.037 · change: 0.000

Affected products

Microsoft Web Media Extensions — versions 1.0.0.0
Microsoft Web Media Extensions

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-28465 (Patch, Vendor Advisory)
www.zerodayinitiative.com/advisories/ZDI-21-572/ (Third Party Advisory)
www.zerodayinitiative.com/advisories/ZDI-21-579/ (Third Party Advisory)

Frequently asked questions

What is CVE-2021-28465?: CVE-2021-28465 is a high-severity vulnerability in Microsoft Web Media Extensions, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2021-05-11.
How severe is CVE-2021-28465?: High severity. CVSS v3 base score is 7.8 out of 10.