CVE-2021-43890
Plain English Summary
AI-powered analysis for quick understanding
This vulnerability allows an attacker to trick users into installing malicious software through specially crafted files, which can lead to infections from malware like Emotet or Trickbot. To exploit this, the attacker must convince the user to open the malicious attachment, and users with administrative rights are at higher risk than those with limited permissions.
Technical 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.
CVSS Vector Analysis
Vector String
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:HExploit Resources
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Official References
Quick Information
Published
Dec 15, 2021
over 4 years ago
Last Modified
Feb 25, 2026
about 1 month ago
Vendor
microsoft
Product
app installer
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