FKIE_CVE-2021-43890

Vulnerability from fkie_nvd - Published: 2021-12-15 15:15 - Updated: 2025-10-30 19:16
Severity ?
7.1 (High) - CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
7.1 (High) - CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Summary
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.
References
secure@microsoft.comhttps://github.com/ChrisTitusTech/winutil/pull/26Issue Tracking
secure@microsoft.comhttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890Patch, Vendor Advisory
secure@microsoft.comhttps://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.htmlPress/Media Coverage, Third Party Advisory
secure@microsoft.comhttps://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/Press/Media Coverage, Third Party Advisory
secure@microsoft.comhttps://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/Exploit, Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108https://github.com/ChrisTitusTech/winutil/pull/26Issue Tracking
af854a3a-2127-422b-91ae-364da2661108https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890Patch, Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.htmlPress/Media Coverage, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/Press/Media Coverage, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890US Government Resource
Impacted products
Vendor Product Version
microsoft app_installer *
microsoft windows_10_1809 -
microsoft windows_10_1903 -
microsoft windows_10_1909 -
microsoft windows_10_2004 -
microsoft windows_10_20h2 -
microsoft windows_10_21h1 -
microsoft windows_10_21h2 -
microsoft windows_11_21h2 -
microsoft app_installer *
microsoft windows_10_1507 -
microsoft windows_10_1709 -
microsoft windows_10_1803 -
To clipboard 

{
  "cisaActionDue": "2021-12-29",
  "cisaExploitAdd": "2021-12-15",
  "cisaRequiredAction": "Apply updates per vendor instructions.",
  "cisaVulnerabilityName": "Microsoft Windows AppX Installer Spoofing Vulnerability",
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  "cveTags": [],
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      "lang": "en",
      "value": "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.\nAn 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.\nPlease 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.\nPlease see the Mitigations and Workaround sections for important information about steps you can take to protect your system from this vulnerability.\nDecember 27 2023 Update:\nIn 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.\nTo address this increase in activity, we have updated the App Installer to disable the ms-appinstaller protocol by default and recommend other potential mitigations.\n"
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad de Suplantaci\u00f3n de Identidad de Windows AppX Installer"
    }
  ],
  "id": "CVE-2021-43890",
  "lastModified": "2025-10-30T19:16:58.980",
  "metrics": {
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        "acInsufInfo": false,
        "baseSeverity": "MEDIUM",
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          "authentication": "SINGLE",
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  "published": "2021-12-15T15:15:11.207",
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}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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