CVE-2021-43890
Microsoft Windows AppX Installer Spoofing Vulnerability - [Actively Exploited]
Description
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.
INFO
Published Date :
Dec. 15, 2021, 3:15 p.m.
Last Modified :
Nov. 21, 2024, 6:29 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CISA KEV (Known Exploited Vulnerabilities)
For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.
Microsoft Windows AppX Installer contains a spoofing vulnerability which has a high impacts to confidentiality, integrity, and availability.
Apply updates per vendor instructions.
https://nvd.nist.gov/vuln/detail/CVE-2021-43890
Affected Products
The following products are affected by CVE-2021-43890
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 2.0 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Microsoft has released an update to address this issue.
Public PoC/Exploit Available at Github
CVE-2021-43890 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2021-43890.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2021-43890 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2021-43890
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Ostorlab KEV: One-command to detect most remotely known exploitable vulnerabilities. Sourced from CISA KEV, Google's Tsunami, Ostorlab's Asteroid and Bug Bounty programs.
cisa-kev vulnerability 0day cisa exploits
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2021-43890 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2021-43890 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Modified Analysis by [email protected]
Mar. 07, 2025
Action Type Old Value New Value Changed CPE Configuration AND OR cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.16 AND OR cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.16 Changed CPE Configuration AND OR cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.16 AND OR cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.16 Changed CPE Configuration AND OR cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.11 AND OR cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.11 Changed CPE Configuration AND OR cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.11 AND OR cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions from (excluding) 1.11 -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 21, 2024
Action Type Old Value New Value Added Reference https://github.com/ChrisTitusTech/winutil/pull/26 Added Reference https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890 Added Reference https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html Added Reference https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/ Added Reference https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/ -
Modified Analysis by [email protected]
Jul. 24, 2024
Action Type Old Value New Value Changed Reference Type https://github.com/ChrisTitusTech/winutil/pull/26 No Types Assigned https://github.com/ChrisTitusTech/winutil/pull/26 Issue Tracking Changed Reference Type https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html No Types Assigned https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html Press/Media Coverage, Third Party Advisory Changed Reference Type https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/ No Types Assigned https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/ Press/Media Coverage, Third Party Advisory Changed Reference Type https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/ No Types Assigned https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/ Exploit, Vendor Advisory Changed CPE Configuration AND OR cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:x64:* cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:x86:* OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* AND OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions up to (excluding) 1.16 OR cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:* Added CPE Configuration AND OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* versions up to (excluding) 1.11 OR cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:* cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:* -
CVE Modified by [email protected]
May. 29, 2024
Action Type Old Value New Value Changed Description <p>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.</p> <p>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.</p> <p>Please see the <strong>Security Updates</strong> table for the link to the updated app. Alternatively you can download and install the Installer using the links provided in the <strong>FAQ</strong> section.</p> <p>Please see the <strong>Mitigations</strong> and <strong>Workaround</strong> sections for important information about steps you can take to protect your system from this vulnerability.</p> <p><strong>December 27 2023 Update:</strong></p> <p>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 <a href="https://learn.microsoft.com/en-us/windows/msix/app-installer/installing-windows10-apps-web">ms-appinstaller URI scheme</a>.</p> <p>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.</p> 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. -
CVE Modified by [email protected]
May. 14, 2024
Action Type Old Value New Value -
CVE Modified by [email protected]
Dec. 30, 2023
Action Type Old Value New Value Added Reference Microsoft Corporation https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/ [No types assigned] Added Reference Microsoft Corporation https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html [No types assigned] Added Reference Microsoft Corporation https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/ [No types assigned] Added Reference Microsoft Corporation https://github.com/ChrisTitusTech/winutil/pull/26 [No types assigned] -
CVE Modified by [email protected]
Dec. 28, 2023
Action Type Old Value New Value Changed Description Windows AppX Installer Spoofing Vulnerability <p>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.</p> <p>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.</p> <p>Please see the <strong>Security Updates</strong> table for the link to the updated app. Alternatively you can download and install the Installer using the links provided in the <strong>FAQ</strong> section.</p> <p>Please see the <strong>Mitigations</strong> and <strong>Workaround</strong> sections for important information about steps you can take to protect your system from this vulnerability.</p> <p><strong>December 27 2023 Update:</strong></p> <p>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 <a href="https://learn.microsoft.com/en-us/windows/msix/app-installer/installing-windows10-apps-web">ms-appinstaller URI scheme</a>.</p> <p>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.</p> -
CWE Remap by [email protected]
Jul. 12, 2022
Action Type Old Value New Value Changed CWE CWE-290 NVD-CWE-noinfo -
Modified Analysis by [email protected]
Jan. 01, 2022
Action Type Old Value New Value -
CVE Modified by [email protected]
Dec. 29, 2021
Action Type Old Value New Value Added CVSS V3.1 Microsoft Corporation AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H -
Initial Analysis by [email protected]
Dec. 23, 2021
Action Type Old Value New Value Added CVSS V2 Metadata Victim must voluntarily interact with attack mechanism Added CVSS V2 NIST (AV:N/AC:M/Au:S/C:P/I:P/A:P) Added CVSS V3.1 NIST AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H Changed Reference Type https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890 No Types Assigned https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890 Patch, Vendor Advisory Added CWE NIST CWE-290 Added CPE Configuration AND OR *cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:* OR cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:x64:* cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:x86:*
Vulnerability Scoring Details
Base CVSS Score: 7.1
Base CVSS Score: 6
Exploit Prediction
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.
14.93 }} -38.95%
score
0.93973
percentile