vciy

CVE-2021-43883

INDEX BUILT · 2026-09-20

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Windows Installer Elevation of Privilege Vulnerability

CVE-2021-438834 of 4 sources documented this
45

rank 45 = 17 + 20 + 0 + 8 + 0

rank@v1 · this cycle

Someone is already using it

CISA KEV catalog · public proof-of-concept · FIRST EPSS

EPSS 0.11963  ·  without this subject the record ranks 28

What it costs you if it fires

NVD CVSS base score, then the CNA's own

CVSS 7.8, from NVD  ·  without this subject the record ranks 25

It is getting worse, not staying still

FIRST EPSS series, rescorings and bad loads removed

no persisting rise in 365 days  ·  without this subject the record ranks 45

How much of the world it touches

NVD CPE configurations

12 products in the CPE ranges  ·  without this subject the record ranks 37

Someone else already set the date

CISA KEV remediation due date

no CISA due date  ·  without this subject the record ranks 45

Unaudited dollar value2 of 3 inputs carry a receipt
Exposure$597,000over the next 30 days, if this record is yours
Movement-$812,000on 2022-02-04, the last material move, 4 years, 4 months before this reading
Basisassumeda published average, not your estate

$597,000 = $4.99M incident cost x 1 exposure x 0.11963 likelihood

udv@v1 · unaudited · wrong for you until you say what you run

$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.

Hindsight · the state

0.11963EPSSNOT IN KEVas of 2026-09-20
Severity7.8 HIGHreceipt
Harmtotal lossreceipt
Exploitationpublic proof-of-conceptreceipt
Defensefix version namedreceipt
Movementthreshold crossedreceipt
PLATEAU10Minimal movement since 2025-03-17, 455 days at 0.12, as of 2026-06-15. arc-rules@v1

Foresight · where to check next

No weakness class or product neighbourhood is held for this record, so this index cannot name anywhere to check next. That is an absence in the record, not a finding about the software.

Color is a claim, not decoration:the hostile worldthe defenseno signal

Running Microsoft Windows 10 Version 1809? Check your version

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Harm, if it fires from the vector and the weakness

Written for the ticket you're about to file.

Reachneeds local access · low privileges required · no user interaction · low attack complexityreceipt
ImpactComplete confidentiality, integrity and availability lossreceipt
Scored fromCVSS v3.1 · the CNA's vectorreceipt
Weakness classNo CWE mapping in held sources.

CISA KEV & Federal Remediation Deadline from the record and CISA

The fix, and how long it's been waiting.

Fixed in10.0.17763.2366; 10.0.18363.1977; 10.0.19043.1415; 10.0.20348.405; 10.0.19041.1415; 10.0.19042.1415; 10.0.22000.376; 10.0.19044.1415; 10.0.10240.19145…receipt
Patch available sinceNo dated patch-availability record in held sources. The index holds reference URLs without dates and only the current revision of the CVE record, so the day a fix first existed cannot be derived. Only the versions it landed in.

Exploit Status & Known PoCs a ladder, not a score

Current rung: Proof-of-concept published · 1 public repository, 2021-12-02.

  • RUNG 1Nothing observed in held sources
  • RUNG 2Proof-of-concept published · 1 public repository2021-12-02receipt
  • RUNG 3Exploited in the wild · CISA KEV listed
  • RUNG 4Ransomware campaign use known

Authority who says so

CVSS, the CNA7.8 HIGHreceipt
CVSS, NVD7.8 HIGHreceipt
Exploit probability0.11963 · top 4% of all CVEsreceipt
Blast breadth3 products across 1 vendorderived
Assigned bymicrosoftreceipt
Recorded changes30 · last 19 Sep 2026derived

Affected & Fixed Versions as published

Affected productMicrosoft Windows 10 Version 1809; Microsoft Windows Server 2019; Microsoft Windows Server 2019 (Server Core installation); Microsoft Windows 10 Version 1909; Microsoft Windows 10 Version 21H1…receipt
Published rangesmicrosoft windows 10 20h2; microsoft windows 10 21h1; microsoft windows 10 21h2; microsoft windows 10 1607receipt
Show all 12 published ranges
microsoft windows 10 20h2
microsoft windows 10 21h1
microsoft windows 10 21h2
microsoft windows 10 1607
microsoft windows 10 1809
microsoft windows 10 1909
microsoft windows 10 2004
microsoft windows server 20h2
microsoft windows server 2022
microsoft windows server 2008 r2
microsoft windows server 2012 r2
microsoft windows server 2016 2004
Fixed in10.0.17763.2366; 10.0.18363.1977; 10.0.19043.1415; 10.0.20348.405; 10.0.19041.1415; 10.0.19042.1415; 10.0.22000.376; 10.0.19044.1415; 10.0.10240.19145…receipt

A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.

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What it is stated by the CNA

Windows Installer Elevation of Privilege Vulnerability receipt

NVD's analysis a second authority

severity
7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
affected versions
microsoft windows 10 20h2; microsoft windows 10 21h1; microsoft windows 10 21h2; and 9 more, listed in full below
also scored by
[email protected] 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

check it yourself portal.msrc.microsoft.com receipt

Dated events

2021-12-24EPSS moved 0.02 to 0.182022-02-04EPSS moved 0.18 to 0.012026-06-15EPSS moved 0.09 to 0.12

Movement the material steps

16 Dec 20210.00416
24 Dec 20210.17642 · crossed 0.10
4 Feb 20220.01372 · crossed 0.10
7 Mar 20234.3e-4 · scoring model v2023.03.01
17 Mar 20250.03139 · scoring model v2025.03.14
15 Jun 20260.11963 · crossed 0.10 · scoring model v2026.06.15

This score more than doubled inside 72 hours. Both observations are in the full history below.

Show all 27 observations
16 Dec 20210.00416
18 Dec 20210.0184
24 Dec 20210.17642
4 Feb 20220.01372
7 Mar 20234.3e-4
8 Mar 20230.00043
17 Dec 20240.00061
17 Mar 20250.03139
19 Mar 20250.06502
20 Mar 20250.0554
27 Mar 20250.06502
28 Mar 20250.0554
29 Mar 20250.06502
30 Mar 20250.0554
17 Apr 20250.05873
5 May 20250.07337
21 May 20250.07816
24 May 20250.08752
1 Oct 20250.09272
27 Oct 20250.08752
28 Oct 20250.09272
18 Nov 20250.0866
21 Nov 20250.09272
27 Dec 20250.08752
28 Dec 20250.09272
17 Mar 20260.09119
15 Jun 20260.11963

27 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt

The full biography

EPSS 0.11963Public PoC2021-12-02Published2021-12-15Index as of2026-06-15

Exploit probability more than doubled between 2021-12-16 and 2021-12-18 (0.00416 → 0.0184) and the record had been public for 4 years, 6 months when this index was last written.

Public PoC 2021-12-02 receipt · Published 2021-12-15 receipt · Index as of 2026-06-15 derived

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