CVE-2021-43890 (GCVE-0-2021-43890)

Vulnerability from cvelistv5 – Published: 2021-12-15 14:15 – Updated: 2025-10-21 23:25
VLAI? CISA KEV
Title
Windows AppX Installer Spoofing Vulnerability
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.
Severity ?
7.1 (High)
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
CWE
  • Spoofing
Assigner
References
Impacted products
Vendor Product Version
Microsoft App Installer Affected: 1.0.0.0 , < publication (custom)
    cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*
 Create a notification for this product.
CISA KEV
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 7325fa1e-f9a9-439f-a507-571262721f42

Vulnerability ID: CVE-2021-43890

Status: Confirmed

Status Updated: 2021-12-15 00:00 UTC

Exploited: Yes

Timestamps
First Seen: 2021-12-15
Asserted: 2021-12-15
Scope
Notes: KEV entry: Microsoft Windows AppX Installer Spoofing Vulnerability | Affected: Microsoft / Windows | Description: Microsoft Windows AppX Installer contains a spoofing vulnerability which has a high impacts to confidentiality, integrity, and availability. | Required action: Apply updates per vendor instructions. | Due date: 2021-12-29 | Known ransomware campaign use (KEV): Known | Notes (KEV): https://nvd.nist.gov/vuln/detail/CVE-2021-43890
Evidence

Type: Vendor Report

Signal: Successful Exploitation

Confidence: 80%

Source: cisa-kev

Details
Cwes
Feed CISA Known Exploited Vulnerabilities Catalog
Product Windows
Due Date 2021-12-29
Date Added 2021-12-15
Vendorproject Microsoft
Vulnerabilityname Microsoft Windows AppX Installer Spoofing Vulnerability
Knownransomwarecampaignuse Known
References
Created: 2026-02-02 12:28 UTC | Updated: 2026-02-06 07:17 UTC
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2024-08-04T04:10:17.079Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://github.com/ChrisTitusTech/winutil/pull/26"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2021-43890",
                "options": [
                  {
                    "Exploitation": "active"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2024-02-26T13:43:15.135020Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          },
          {
            "other": {
              "content": {
                "dateAdded": "2021-12-15",
                "reference": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890"
              },
              "type": "kev"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "description": "CWE-noinfo Not enough information",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-10-21T23:25:22.309Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "government-resource"
            ],
            "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890"
          }
        ],
        "timeline": [
          {
            "lang": "en",
            "time": "2021-12-15T00:00:00+00:00",
            "value": "CVE-2021-43890 added to CISA KEV"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "cpes": [
            "cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*"
          ],
          "platforms": [
            "Unknown"
          ],
          "product": "App Installer",
          "vendor": "Microsoft",
          "versions": [
            {
              "lessThan": "publication",
              "status": "affected",
              "version": "1.0.0.0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "datePublic": "2021-12-14T08:00:00.000Z",
      "descriptions": [
        {
          "lang": "en-US",
          "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"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en-US",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "Spoofing",
              "lang": "en-US",
              "type": "Impact"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2024-05-29T14:44:37.753Z",
        "orgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
        "shortName": "microsoft"
      },
      "references": [
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890"
        },
        {
          "url": "https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/"
        },
        {
          "url": "https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html"
        },
        {
          "url": "https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/"
        },
        {
          "url": "https://github.com/ChrisTitusTech/winutil/pull/26"
        }
      ],
      "title": "Windows AppX Installer Spoofing Vulnerability"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f38d906d-7342-40ea-92c1-6c4a2c6478c8",
    "assignerShortName": "microsoft",
    "cveId": "CVE-2021-43890",
    "datePublished": "2021-12-15T14:15:35.000Z",
    "dateReserved": "2021-11-16T00:00:00.000Z",
    "dateUpdated": "2025-10-21T23:25:22.309Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "cisa_known_exploited": {
      "cveID": "CVE-2021-43890",
      "dateAdded": "2021-12-15",
      "dueDate": "2021-12-29",
      "knownRansomwareCampaignUse": "Known",
      "notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-43890",
      "product": "Windows",
      "requiredAction": "Apply updates per vendor instructions.",
      "shortDescription": "Microsoft Windows AppX Installer contains a spoofing vulnerability which has a high impacts to confidentiality, integrity, and availability.",
      "vendorProject": "Microsoft",
      "vulnerabilityName": "Microsoft Windows AppX Installer Spoofing Vulnerability"
    },
    "fkie_nvd": {
      "cisaActionDue": "2021-12-29",
      "cisaExploitAdd": "2021-12-15",
      "cisaRequiredAction": "Apply updates per vendor instructions.",
      "cisaVulnerabilityName": "Microsoft Windows AppX Installer Spoofing Vulnerability",
      "configurations": "[{\"operator\": \"AND\", \"nodes\": [{\"operator\": \"OR\", \"negate\": false, \"cpeMatch\": [{\"vulnerable\": true, \"criteria\": \"cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*\", \"versionEndExcluding\": \"1.16\", \"matchCriteriaId\": \"F5F1F637-0D18-4CBE-A56B-DEA530ACC1B0\"}]}, {\"operator\": \"OR\", \"negate\": false, \"cpeMatch\": [{\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"2E332666-2E03-468E-BC30-299816D6E8ED\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"A363CE8F-F399-4B6E-9E7D-349792F95DDB\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"A1B570A8-ED1A-46B6-B8AB-064445F8FC4C\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"D4DBE5B2-AE10-4251-BCDA-DC5EDEE6EE67\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"6AFD13A6-A390-4400-9029-2F4058CA17E2\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"B1FED4C9-B680-4F44-ADC0-AC43D6B5F184\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"2F513002-D8C1-4D3A-9F79-4B52498F67E9\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"BB4AE761-6FAC-4000-A63D-42CE3FAB8412\"}]}]}, {\"operator\": \"AND\", \"nodes\": [{\"operator\": \"OR\", \"negate\": false, \"cpeMatch\": [{\"vulnerable\": true, \"criteria\": \"cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*\", \"versionEndExcluding\": \"1.11\", \"matchCriteriaId\": \"62B0A730-2442-4C85-8CFA-098D4DADFF8C\"}]}, {\"operator\": \"OR\", \"negate\": false, \"cpeMatch\": [{\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"542DAEEC-73CC-46C6-A630-BF474A3446AC\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"AC160B20-3EA0-49A0-A857-4E7A1C2D74E2\"}, {\"vulnerable\": false, \"criteria\": \"cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:*\", \"matchCriteriaId\": \"00345596-E9E0-4096-8DC6-0212F4747A13\"}]}]}]",
      "descriptions": "[{\"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": "2024-11-21T06:29:59.457",
      "metrics": "{\"cvssMetricV31\": [{\"source\": \"secure@microsoft.com\", \"type\": \"Secondary\", \"cvssData\": {\"version\": \"3.1\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H\", \"baseScore\": 7.1, \"baseSeverity\": \"HIGH\", \"attackVector\": \"NETWORK\", \"attackComplexity\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"userInteraction\": \"REQUIRED\", \"scope\": \"UNCHANGED\", \"confidentialityImpact\": \"HIGH\", \"integrityImpact\": \"HIGH\", \"availabilityImpact\": \"HIGH\"}, \"exploitabilityScore\": 1.2, \"impactScore\": 5.9}, {\"source\": \"nvd@nist.gov\", \"type\": \"Primary\", \"cvssData\": {\"version\": \"3.1\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H\", \"baseScore\": 7.1, \"baseSeverity\": \"HIGH\", \"attackVector\": \"NETWORK\", \"attackComplexity\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"userInteraction\": \"REQUIRED\", \"scope\": \"UNCHANGED\", \"confidentialityImpact\": \"HIGH\", \"integrityImpact\": \"HIGH\", \"availabilityImpact\": \"HIGH\"}, \"exploitabilityScore\": 1.2, \"impactScore\": 5.9}], \"cvssMetricV2\": [{\"source\": \"nvd@nist.gov\", \"type\": \"Primary\", \"cvssData\": {\"version\": \"2.0\", \"vectorString\": \"AV:N/AC:M/Au:S/C:P/I:P/A:P\", \"baseScore\": 6.0, \"accessVector\": \"NETWORK\", \"accessComplexity\": \"MEDIUM\", \"authentication\": \"SINGLE\", \"confidentialityImpact\": \"PARTIAL\", \"integrityImpact\": \"PARTIAL\", \"availabilityImpact\": \"PARTIAL\"}, \"baseSeverity\": \"MEDIUM\", \"exploitabilityScore\": 6.8, \"impactScore\": 6.4, \"acInsufInfo\": false, \"obtainAllPrivilege\": false, \"obtainUserPrivilege\": false, \"obtainOtherPrivilege\": false, \"userInteractionRequired\": true}]}",
      "published": "2021-12-15T15:15:11.207",
      "references": "[{\"url\": \"https://github.com/ChrisTitusTech/winutil/pull/26\", \"source\": \"secure@microsoft.com\", \"tags\": [\"Issue Tracking\"]}, {\"url\": \"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890\", \"source\": \"secure@microsoft.com\", \"tags\": [\"Patch\", \"Vendor Advisory\"]}, {\"url\": \"https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html\", \"source\": \"secure@microsoft.com\", \"tags\": [\"Press/Media Coverage\", \"Third Party Advisory\"]}, {\"url\": \"https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/\", \"source\": \"secure@microsoft.com\", \"tags\": [\"Press/Media Coverage\", \"Third Party Advisory\"]}, {\"url\": \"https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/\", \"source\": \"secure@microsoft.com\", \"tags\": [\"Exploit\", \"Vendor Advisory\"]}, {\"url\": \"https://github.com/ChrisTitusTech/winutil/pull/26\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Issue Tracking\"]}, {\"url\": \"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Patch\", \"Vendor Advisory\"]}, {\"url\": \"https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Press/Media Coverage\", \"Third Party Advisory\"]}, {\"url\": \"https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Press/Media Coverage\", \"Third Party Advisory\"]}, {\"url\": \"https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/\", \"source\": \"af854a3a-2127-422b-91ae-364da2661108\", \"tags\": [\"Exploit\", \"Vendor Advisory\"]}]",
      "sourceIdentifier": "secure@microsoft.com",
      "vulnStatus": "Modified",
      "weaknesses": "[{\"source\": \"nvd@nist.gov\", \"type\": \"Primary\", \"description\": [{\"lang\": \"en\", \"value\": \"NVD-CWE-noinfo\"}]}]"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2021-43890\",\"sourceIdentifier\":\"secure@microsoft.com\",\"published\":\"2021-12-15T15:15:11.207\",\"lastModified\":\"2025-10-30T19:16:58.980\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"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\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"secure@microsoft.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H\",\"baseScore\":7.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"REQUIRED\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.2,\"impactScore\":5.9},{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H\",\"baseScore\":7.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"REQUIRED\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.2,\"impactScore\":5.9}],\"cvssMetricV2\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"2.0\",\"vectorString\":\"AV:N/AC:M/Au:S/C:P/I:P/A:P\",\"baseScore\":6.0,\"accessVector\":\"NETWORK\",\"accessComplexity\":\"MEDIUM\",\"authentication\":\"SINGLE\",\"confidentialityImpact\":\"PARTIAL\",\"integrityImpact\":\"PARTIAL\",\"availabilityImpact\":\"PARTIAL\"},\"baseSeverity\":\"MEDIUM\",\"exploitabilityScore\":6.8,\"impactScore\":6.4,\"acInsufInfo\":false,\"obtainAllPrivilege\":false,\"obtainUserPrivilege\":false,\"obtainOtherPrivilege\":false,\"userInteractionRequired\":true}]},\"cisaExploitAdd\":\"2021-12-15\",\"cisaActionDue\":\"2021-12-29\",\"cisaRequiredAction\":\"Apply updates per vendor instructions.\",\"cisaVulnerabilityName\":\"Microsoft Windows AppX Installer Spoofing Vulnerability\",\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"NVD-CWE-noinfo\"}]}],\"configurations\":[{\"operator\":\"AND\",\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"1.16\",\"matchCriteriaId\":\"F5F1F637-0D18-4CBE-A56B-DEA530ACC1B0\"}]},{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_1809:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"2E332666-2E03-468E-BC30-299816D6E8ED\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_1903:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"A363CE8F-F399-4B6E-9E7D-349792F95DDB\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_1909:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"A1B570A8-ED1A-46B6-B8AB-064445F8FC4C\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_2004:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"D4DBE5B2-AE10-4251-BCDA-DC5EDEE6EE67\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_20h2:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"6AFD13A6-A390-4400-9029-2F4058CA17E2\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_21h1:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"B1FED4C9-B680-4F44-ADC0-AC43D6B5F184\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_21h2:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"2F513002-D8C1-4D3A-9F79-4B52498F67E9\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_11_21h2:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"BB4AE761-6FAC-4000-A63D-42CE3FAB8412\"}]}]},{\"operator\":\"AND\",\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"1.11\",\"matchCriteriaId\":\"62B0A730-2442-4C85-8CFA-098D4DADFF8C\"}]},{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_1507:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"542DAEEC-73CC-46C6-A630-BF474A3446AC\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_1709:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"AC160B20-3EA0-49A0-A857-4E7A1C2D74E2\"},{\"vulnerable\":false,\"criteria\":\"cpe:2.3:o:microsoft:windows_10_1803:-:*:*:*:*:*:*:*\",\"matchCriteriaId\":\"00345596-E9E0-4096-8DC6-0212F4747A13\"}]}]}],\"references\":[{\"url\":\"https://github.com/ChrisTitusTech/winutil/pull/26\",\"source\":\"secure@microsoft.com\",\"tags\":[\"Issue Tracking\"]},{\"url\":\"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890\",\"source\":\"secure@microsoft.com\",\"tags\":[\"Patch\",\"Vendor Advisory\"]},{\"url\":\"https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html\",\"source\":\"secure@microsoft.com\",\"tags\":[\"Press/Media Coverage\",\"Third Party Advisory\"]},{\"url\":\"https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/\",\"source\":\"secure@microsoft.com\",\"tags\":[\"Press/Media Coverage\",\"Third Party Advisory\"]},{\"url\":\"https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/\",\"source\":\"secure@microsoft.com\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]},{\"url\":\"https://github.com/ChrisTitusTech/winutil/pull/26\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Issue Tracking\"]},{\"url\":\"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Patch\",\"Vendor Advisory\"]},{\"url\":\"https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Press/Media Coverage\",\"Third Party Advisory\"]},{\"url\":\"https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Press/Media Coverage\",\"Third Party Advisory\"]},{\"url\":\"https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]},{\"url\":\"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890\",\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"tags\":[\"US Government Resource\"]}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890\", \"tags\": [\"x_refsource_MISC\", \"x_transferred\"]}, {\"url\": \"https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://github.com/ChrisTitusTech/winutil/pull/26\", \"tags\": [\"x_transferred\"]}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2024-08-04T04:10:17.079Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2021-43890\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"active\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2024-02-26T13:43:15.135020Z\"}}}, {\"other\": {\"type\": \"kev\", \"content\": {\"dateAdded\": \"2021-12-15\", \"reference\": \"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890\"}}}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2021-12-15T00:00:00+00:00\", \"value\": \"CVE-2021-43890 added to CISA KEV\"}], \"references\": [{\"url\": \"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43890\", \"tags\": [\"government-resource\"]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"description\": \"CWE-noinfo Not enough information\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2025-02-04T16:04:44.546Z\"}}], \"cna\": {\"title\": \"Windows AppX Installer Spoofing Vulnerability\", \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 7.1, \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C\"}, \"scenarios\": [{\"lang\": \"en-US\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:microsoft:app_installer:*:*:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"App Installer\", \"versions\": [{\"status\": \"affected\", \"version\": \"1.0.0.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"Unknown\"]}], \"datePublic\": \"2021-12-14T08:00:00.000Z\", \"references\": [{\"url\": \"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43890\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://www.bleepingcomputer.com/news/microsoft/microsoft-disables-msix-protocol-handler-abused-in-malware-attacks/\"}, {\"url\": \"https://thehackernews.com/2023/12/microsoft-disables-msix-app-installer.html\"}, {\"url\": \"https://www.microsoft.com/en-us/security/blog/2023/12/28/financially-motivated-threat-actors-misusing-app-installer/\"}, {\"url\": \"https://github.com/ChrisTitusTech/winutil/pull/26\"}], \"descriptions\": [{\"lang\": \"en-US\", \"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\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en-US\", \"type\": \"Impact\", \"description\": \"Spoofing\"}]}], \"providerMetadata\": {\"orgId\": \"f38d906d-7342-40ea-92c1-6c4a2c6478c8\", \"shortName\": \"microsoft\", \"dateUpdated\": \"2024-05-29T14:44:37.753Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-43890\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-10-21T23:25:22.309Z\", \"dateReserved\": \"2021-11-16T00:00:00.000Z\", \"assignerOrgId\": \"f38d906d-7342-40ea-92c1-6c4a2c6478c8\", \"datePublished\": \"2021-12-15T14:15:35.000Z\", \"assignerShortName\": \"microsoft\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • 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.



Detection rules are retrieved from Rulezet.