What is the CVSS score of CVE-2021-43890?

CVE-2021-43890 has a CVSS 3.1 base score of 7.1 (High). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H. EPSS exploitation probability: 10.3%.

Is there a public PoC exploit available for CVE-2021-43890?

Yes, a public proof-of-concept exploit is available for CVE-2021-43890. Prioritise patching immediately. EPSS: 10.3%.

Is there a patch available for CVE-2021-43890?

Yes, a patch is available for CVE-2021-43890. Update the affected software to the latest version immediately.

App Installer CVE-2021-43890

HIGH

2021-12-15 secure@microsoft.com

Information Disclosure Microsoft App Installer

7.1

CVSS 3.1 · NVD

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Vulnerability Assessment

Impact	CVSS score of 7.1 (HIGH). Attack characteristics: network attack vector, high complexity, low privileges required, user interaction required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the high-severity affected system.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 10.3% exploitation probability (EPSS)

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AnalysisAI

We have investigated reports of a spoofing vulnerability in AppX installer that affects Microsoft Windows. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable. Public exploit code available.

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

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Technical ContextAI · show details

We have investigated reports of a spoofing vulnerability in AppX installer that affects Microsoft Windows. Microsoft is aware of attacks that attempt to exploit this vulnerability by using specially crafted packages that include the malware family known as Emotet/Trickbot/Bazaloader. An attacker could craft a malicious attachment to be used in phishing campaigns. The attacker would then have to convince the user to open the specially crafted attachment. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. Please see the Security Updates table for the link to the updated app. Alternatively you can download and install the Installer using the links provided in the FAQ section. Please see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability. December 27 2023 Update: In recent months, Microsoft Threat Intelligence has seen an increase in activity from threat actors leveraging social engineering and phishing techniques to target Windows OS users and utilizing the ms-appinstaller URI scheme. To address this increase in activity, we have updated the App Installer to disable the ms-appinstaller protocol by default and recommend other potential mitigations. Affected products include: Microsoft App Installer.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.1 HIGH

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

High

Privileges Required

Low

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Jul 14, 2026 - 04:22 CISA

CVE Published

Dec 15, 2021 - 15:15 nvd

HIGH 7.1

DescriptionNVD

Threat Intelligence Overview

Threat Score

4.7/10

Composite threat intelligence

EPSS Score

10.3%

Top 5% exploitable

Exploit

POC

Public exploit code exists

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

CISA KEV

EPSS

GitHub

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 Yes

EPSS 10.3%

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

Open

Automatable· derived

Human Impact· derived

High

Priority Score

116

Low Medium High Critical

KEV: +50

EPSS: +10

CVSS: +36

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.