Vulnerability

CVE-2021-1647

High· 7.8KEVCVSS7.8EPSS76%

.rules3/5

Microsoft Defender Remote Code Execution Vulnerability

Microsoft Defender contains an unspecified vulnerability that allows for remote code execution.

Threat signal

99/100

Severe

Severity

high

CVSS

7.8

EPSS

76%

Active

KEV

CISA KEV — actively exploited

1669d overdue

AffectedMicrosoft — Defender

Added to KEV

2021-11-03

Federal patch due (BOD 22-01)

2021-11-17

Required action (CISA verbatim)

Apply updates per vendor instructions.

Vendor advisory + references

https://nvd.nist.gov/vuln/detail/CVE-2021-1647

CISA description: “Microsoft Defender contains an unspecified vulnerability that allows for remote code execution.”

CVSS

v3.1Open in FIRST calculator →

7.8/ 10HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack VectorLocalRequires local access — shell, console, or local app.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredLowStandard user privileges sufficient.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactHighTotal compromise of integrity — full data modification possible.
Availability ImpactHighTotal loss of availability — full DoS possible.

EPSS

Exploit prediction · 30-day horizonFIRST.org →

76.1%

probability of exploitation in next 30 days

p99

higher than 99% of all CVEs

3-day trend↑ 0pp

Statistically about to be weaponized — top-tier triage urgency.

Vendor VEX

No VEX statements published for CVE-2021-1647. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCAct

Active exploitation with total impact on essential/support systems

exploitation: active
automatable: no
impact: total
mission: support

Lifecycle

2021-11-03Added to CISA KEVransomware: Unknown
2021-11-03Published
2021-11-17Federal patch due (BOD 22-01)
2026-06-12Last modified1 source

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.