AEGLIX vulnerability intelligence
CVE-2021-43890
HIGH · CVSS 7.1 · Analyzed
Published: 2021-12-15 · Updated: 2026-08-06 · Source: NVD
Vulnerability overview
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.
Severity and scoring
- CVSS score
- 7.1 · HIGH
- CVSS version
- 3.1
- CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
- Weaknesses
- NVD-CWE-noinfo
CVSS measures technical severity; it does not establish whether this vulnerability is being exploited in your environment.
Known exploitation and remediation
Listed in CISA’s Known Exploited Vulnerabilities catalog.
- Affected product
- Microsoft · Windows
- Added to catalog
- 2021-12-15
- Required action
- Apply updates per vendor instructions.
- CISA remediation due date
- 2021-12-29
CISA deadlines apply to the organizations covered by its directives. Confirm your own remediation requirements.
Verify affected versions and patch availability in the vendor advisory before making changes.
Affected products and versions
cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*
Before (exclusive): 1.16
cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*
Before (exclusive): 1.11
These are NVD CPE applicability entries. Some products depend on configuration conditions; consult the official record to confirm applicability.
Advisories and references
- https://github.com/ChrisTitusTech/winutil/pull/26
Issue Tracking
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890
Patch · Vendor Advisory
- https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html
Press/Media Coverage · Third Party Advisory
- https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/
Press/Media Coverage · Third Party Advisory
- https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/
Exploit · Vendor Advisory
- https://github.com/ChrisTitusTech/winutil/pull/26
Issue Tracking
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890
Patch · Vendor Advisory
- https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html
Press/Media Coverage · Third Party Advisory
- https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/
Press/Media Coverage · Third Party Advisory
- https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/
Exploit · Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890
US Government Resource