CVE-2021-43890
Exploitation confirmed. First attested on 2021-12-15 by CISA-ADP, CISA KEV, GCVE · kevintel.
- Published2021-12-15
- Fixed in1.16 · 1.11
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
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.
Timeline
dates in UTCObserved activity
isMalicious corpus · updated 2026-11-04 09:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-43890?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-43890?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 1.16 | < 1.16 | 1.16 | NVD |
| 1.11 | < 1.11 | 1.11 | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Products declared by the CNA1 product
As microsoft, the CNA that assigned this CVE, declared them in the CVE record; versions as written.
- Microsoft App Installer
platforms: Unknown
Affected- ≥ 1.0.0.0, < publicationfixed in publicationcustom
Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2024-05-29
Fix
- Update Microsoft app installer to 1.16 · 1.11
- CISA’s required action: Apply updates per vendor instructions.due 2021-12-29
Advisories and patches
- portal.msrc.microsoft.comPatch · Vendor Advisory
- www.microsoft.comVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
- Metasploit modules
- none listed Metasploit Framework
CISA Known Exploited Vulnerability
- Date Added
- 2021-12-15
- Patch Due Date
- 2021-12-29
- Ransomware Use
- Known
- Required Action
- Apply updates per vendor instructions.
Sources
- CISA KEVKEV entry2021-12-15
- ENISA EUVDexploitation2021-12-152021-12-15
- GCVEexploitation2021-12-15
- CISA-ADPSSVC decisionactive2026-08-05
- OpenCVESSVC decisionactive—
- CNACVSS 3.17.1known since 2026-10-23
- NVDCVSS 3.17.1read 2026-10-23
- NVDCVSS 2.06read 2026-10-23
- FIRST EPSSEPSS score11.3 %read 2026-11-03
- GitHub Advisoriesadvisory—
Identifiers
- EUVD-2021-30752same flawENISA EUVD · LicenseRef-ENISA-legal-notice
- GHSA-hvcq-2mcq-rg5fsame flawGitHub Advisory Database · CC-BY-4.0
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
- Published
- 2021-12-15
- Last Modified
- 2026-08-06
- NVD status
- Analyzed
- GitHub Advisory
- GHSA-hvcq-2mcq-rg5f
Frequently asked questions
What is CVE-2021-43890?
Is CVE-2021-43890 actively exploited?
What is the CVSS score for CVE-2021-43890?
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.
Sources for this record
- CISA KEV · CC0-1.0 (cisagov/kev-data)
- CVE Program · CVE Program Terms of Use
- ENISA EU Vulnerability Database · ENISA legal notice §1.2 (reproduction authorised, provided the source is acknowledged)
- FIRST EPSS · EPSS terms of use (free use, attribution requested)
- GCVE · GCVE dump terms (preserve source attribution)
- GitHub Advisory Database · CC-BY-4.0 · GHSA-hvcq-2mcq-rg5f
- NVD · Public domain (17 U.S.C. § 105) for NVD-authored data; third-party content under its own terms
- OpenCVE · OpenCVE terms of service · terms restrict redistribution
- CISA Vulnrichment · CC0-1.0