CVE-2021-34478

Name: CVE-2021-34478
Creator: NVD / NIST
Published: 2021-08-12T18:15:09.003+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 54.38%

Last modified Jun 17, 2026

CVE-2021-34478 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. Microsoft Office Remote Code Execution Vulnerability. EPSS estimates a 54.38% chance of exploitation in the next 30 days.

Description

Microsoft Office Remote Code Execution Vulnerability

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Probability

54.38%

98.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Microsoft	365 Apps	All versions
Microsoft	Office	2019

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34478Patch, Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-1024/Third Party Advisory, VDB Entry
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34478Patch, Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-1024/Third Party Advisory, VDB Entry

Timeline

Published: Aug 12, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-34478?

Microsoft Office Remote Code Execution Vulnerability

How severe is CVE-2021-34478?

CVE-2021-34478 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 54.38% probability of exploitation in the next 30 days.

How do I fix CVE-2021-34478?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-34478?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST