7.8

CVE-2021-1647: Microsoft Defender Remote Code Execution Vulnerability

CVSS: 7.8v3.1HighKEVAnalyzed
Published 12-01-2021Last modified 21-10-2025
Open JSON

Vulnerability summary

CVE-2021-1647 is a high (CVSS 7.8) vulnerability in Microsoft Defender. It is known to be exploited: CISA lists it, first on 03-11-2021. EPSS estimates a 39.65% chance of exploitation in the next 30 days, higher than 98.6% of scored vulnerabilities.

Overall risk
85/100
0100
Critical · default modelHow is this calculated?
CVSS score
7.8/10
010
High · v3.1 (CVE.org)
EPSS score
39.65%
0%100%
High · +0.26 pp in 30 days
KEVListedCISA
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 12-01-2021
    PublishedVulnerability first disclosed.
  2. 03-11-2021
    Added to CISA KEVMicrosoft Defender Remote Code Execution Vulnerability
  3. 17-11-2021
    CISA remediation dueApply updates per vendor instructions.
  4. 21-10-2025
    Last modifiedVulnerability information updated.

Description

Microsoft Defender Remote Code Execution Vulnerability

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

39.65%

Chance of exploitation in the next 30 days

Percentile

99%

Versus all other CVEs

30-day change

+0.26 pp

From 39.39% on 18-09-2026

18-09-202618-10-2026
EPSS score
39.65%

Known exploited

Compare KEV catalogs
CISA KEVListed
Added
03-11-2021
Federal due date
17-11-2021

CISA required action

Apply updates per vendor instructions. nvd.nist.gov/vuln/detail/CVE-2021-1647

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Microsoft7 products

1 vendor · 7 products

References

3 links