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CVE-2021-43890

High

85.6

RPS

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…

Source: NVD

Signals

CVSS
7.1
High · v3.1
EPSS
10.29%
Probability of exploitation in the next 30 days (FIRST)
CISA KEV
In CISA KEV since Dec 2021
Fix commit
No known fix commit
Sources: MoreFixes, FreshFixes
Weakness
Not mapped
Published
15 Dec 2021
Last modified 6 Aug 2026

How to read these signals: RPS · EPSS · CISA KEV · Data sources

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Data as of 7 Oct 2026, 05:16 UK time

CVE-2021-43890 · RPS 85.6 · DevSecure Intelligence