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Security Essentials CVE-2021-1647

HIGH
2021-01-12 secure@microsoft.com
7.8
CVSS 3.1 · Vendor: microsoft
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Vulnerability Assessment

Impact

CVSS score of 7.8 (HIGH). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required.

Exploit ScenarioDerived

Successful exploitation could compromise the high-severity affected system.

This Week Schedule remediation this week. Why: In CISA KEV with patch available.
Exploited in the wild (CISA KEV) Patch available 39.7% exploitation probability (EPSS)

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AnalysisAI

Microsoft Defender Remote Code Execution Vulnerability. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Affected products include: Microsoft Windows Defender, Microsoft Security Essentials, Microsoft System Center Endpoint Protection.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Added to CISA KEV
Jul 14, 2026 - 04:22 CISA
CVE Published
Jan 12, 2021 - 20:15 cve.org
HIGH 7.8

DescriptionCVE.org

Microsoft Defender Remote Code Execution Vulnerability

Threat Intelligence Overview

EPSS Score
39.7%
Top 2% exploitable
Data Quality
2 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV Yes
Public POC No
EPSS 39.7%
Patch available Yes
Active threat Yes
Deciding rule
In CISA KEV with patch available
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Out-of-Cycle
Exploitation· derived
Active
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
High

Priority Score

129
Low Medium High Critical
KEV: +50
EPSS: +40
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)CVE.org

cpe:2.3:a:microsoft:windows_defender:-:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:security_essentials:-:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:system_center_endpoint_protection:-:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:system_center_endpoint_protection:2012:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:system_center_endpoint_protection:2012:r2:*:*:*:*:*:*
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