// For flags

CVE-2021-43890

Microsoft Windows AppX Installer Spoofing Vulnerability

Severity Score

7.1
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

Yes
*KEV

Decision

-
*SSVC
Descriptions

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.

Una vulnerabilidad de SuplantaciĆ³n de Identidad de Windows AppX Installer

Microsoft Windows AppX Installer contains a spoofing vulnerability which has a high impacts to confidentiality, integrity, and availability.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Attack Vector
Network
Attack Complexity
Medium
Authentication
Single
Confidentiality
Partial
Integrity
Partial
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-11-16 CVE Reserved
  • 2021-12-15 CVE Published
  • 2021-12-15 Exploited in Wild
  • 2021-12-29 KEV Due Date
  • 2024-08-04 CVE Updated
  • 2024-08-04 First Exploit
  • 2024-08-17 EPSS Updated
CWE
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 1809
Search vendor "Microsoft" for product "Windows 10 1809"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 1903
Search vendor "Microsoft" for product "Windows 10 1903"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 1909
Search vendor "Microsoft" for product "Windows 10 1909"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 2004
Search vendor "Microsoft" for product "Windows 10 2004"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 20h2
Search vendor "Microsoft" for product "Windows 10 20h2"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 21h1
Search vendor "Microsoft" for product "Windows 10 21h1"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 21h2
Search vendor "Microsoft" for product "Windows 10 21h2"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.16
Search vendor "Microsoft" for product "App Installer" and version " < 1.16"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 11 21h2
Search vendor "Microsoft" for product "Windows 11 21h2"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.11
Search vendor "Microsoft" for product "App Installer" and version " < 1.11"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 1507
Search vendor "Microsoft" for product "Windows 10 1507"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.11
Search vendor "Microsoft" for product "App Installer" and version " < 1.11"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 1709
Search vendor "Microsoft" for product "Windows 10 1709"
--
Safe
Microsoft
Search vendor "Microsoft"
App Installer
Search vendor "Microsoft" for product "App Installer"
< 1.11
Search vendor "Microsoft" for product "App Installer" and version " < 1.11"
-
Affected
in Microsoft
Search vendor "Microsoft"
Windows 10 1803
Search vendor "Microsoft" for product "Windows 10 1803"
--
Safe