Vulnerability Monitor

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CVE-2021-43890

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.

Published

2021-12-15T15:15:11.207

Last Modified

2025-03-07T22:01:51.677

Status

Analyzed

Source

[email protected]

Severity

CVSSv3.1: 7.1 (HIGH)

CVSSv2 Vector

AV:N/AC:M/Au:S/C:P/I:P/A:P

  • Access Vector: NETWORK
  • Access Complexity: MEDIUM
  • Authentication: SINGLE
  • Confidentiality Impact: PARTIAL
  • Integrity Impact: PARTIAL
  • Availability Impact: PARTIAL
Exploitability Score

6.8

Impact Score

6.4

Weaknesses
  • Type: Primary
    NVD-CWE-noinfo
Affected Vendors & Products
Type Vendor Product Version/Range Vulnerable?
Application microsoft app_installer < 1.16 Yes
Operating System microsoft windows_10_1809 - No
Operating System microsoft windows_10_1903 - No
Operating System microsoft windows_10_1909 - No
Operating System microsoft windows_10_2004 - No
Operating System microsoft windows_10_20h2 - No
Operating System microsoft windows_10_21h1 - No
Operating System microsoft windows_10_21h2 - No
Operating System microsoft windows_11_21h2 - No
Application microsoft app_installer < 1.11 Yes
Operating System microsoft windows_10_1507 - No
Operating System microsoft windows_10_1709 - No
Operating System microsoft windows_10_1803 - No
References