What is CVE-2021-38653?

CVE-2021-38653 is a high-severity vulnerability in Microsoft 365 Apps, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2021-09-15.

How severe is CVE-2021-38653?

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

Buffer overflow in Microsoft 365 Apps

CVE-2021-38653

Microsoft Office Visio Remote Code Execution Vulnerability

Vulnerability class: Buffer Overflow

Published 2021-09-15 · last modified 2026-08-10.

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: 0.063 (93.4th percentile), scored 2026-10-07.

Low probability of exploitation in the next 30 days, but still tracked. 93rd percentile — 93.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.063 · newest: 0.063 · change: 0.000

Affected products

Microsoft 365 Apps
Microsoft 365 Apps For Enterprise — versions 16.0.1
Microsoft Office 2019 — versions 19.0.0
Microsoft Office — versions 2019

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

af854a3a-2127-422b-91ae-364da2661108 (Patch, Vendor Advisory)
af854a3a-2127-422b-91ae-364da2661108 (Third Party Advisory, VDB Entry)
msrc.microsoft.com/update-guide/vulnerability/CVE-2021-38653 (vendor-advisory, patch)

Frequently asked questions

What is CVE-2021-38653?: CVE-2021-38653 is a high-severity vulnerability in Microsoft 365 Apps, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2021-09-15.
How severe is CVE-2021-38653?: High severity. CVSS v3 base score is 7.8 out of 10.