vciy

CVE-2021-42278

INDEX BUILT · 2026-09-20

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Active Directory Domain Services Elevation of Privilege Vulnerability

CVE-2021-422784 of 4 sources documented this
69

rank 69 = 40 + 16 + 0 + 7 + 6

rank@v1 · this cycle

Someone is already using it

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

EPSS 0.73297 · CISA KEV listed  ·  without this subject the record ranks 29

What it costs you if it fires

NVD CVSS base score, then the CNA's own

CVSS 6.5, from NVD  ·  without this subject the record ranks 53

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 69

How much of the world it touches

NVD CPE configurations

7 products in the CPE ranges  ·  without this subject the record ranks 62

Someone else already set the date

CISA KEV remediation due date

CISA remediation date held  ·  without this subject the record ranks 63

Unaudited dollar value2 of 3 inputs carry a receipt
Exposure$3.66Mover the next 30 days, if this record is yours
Movement-$2.89Mon 2024-07-04, the last material move, 2 years, 2 months before this reading
Basisassumeda published average, not your estate

$3.66M = $4.99M incident cost x 1 exposure x 0.73297 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

0.73297EPSSKEV · LISTED
Severity7.5 HIGHreceipt
Harmtotal loss · ransomware-linkedreceipt
Exploitationransomware use knownreceipt
Defensefix version namedreceipt
Movementdoubled within 72hreceipt
PLATEAU10Minimal movement since 2026-06-15, 81 days at 0.73, as of 2026-09-04. 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

Sources disagree here.

Severity score
Microsoft7.5 HIGHreceipt
NVD6.5 MEDIUMreceipt
Scoring standard
MicrosoftCVSS v3.1receipt
NVDCVSS v2.0receipt

Both shown, dated. We don't pick winners. disagreement-rules@v1

Running Microsoft Windows Server 2008 R2 Service…? 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.

Reachnetwork-reachable · low privileges required · no user interaction · high attack complexityreceipt
ImpactComplete confidentiality, integrity and availability lossreceipt
Scored fromCVSS v3.1 · the CNA's vectorreceipt
Weakness classNo CWE mapping in held sources.
Ransomware campaign useKnown (CISA)receipt

CISA KEV & Federal Remediation Deadline from the record and CISA

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

Fixed in6.1.7601.25769; 6.0.6003.21282; 6.2.9200.23517; 6.3.9600.20174; 10.0.14393.4770; 10.0.17763.2300; 10.0.20348.350; 10.0.19041.1348; 10.0.19042.1348receipt
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.
CISA remediation statusoverdue since 2022-05-02receipt
CISA required actionApply updates per vendor instructions.receipt
Published to CISA KEV152 daysderived

Exploit Status & Known PoCs a ladder, not a score

Current rung: Ransomware campaign use known, 2022-04-11.

  • RUNG 1Nothing observed in held sources
  • RUNG 2Proof-of-concept published · 6 public repositories2021-12-11receipt
  • RUNG 3Exploited in the wild · CISA KEV listed2022-04-11receipt
  • RUNG 4Ransomware campaign use known2022-04-11receipt

Authority who says so

CVSS, the CNA7.5 HIGHreceipt
CVSS, NVD6.5 MEDIUMreceipt
Exploit probability0.73297 · top 0.56% of all CVEsreceipt
Blast breadth2 products across 1 vendorderived
Assigned bymicrosoftreceipt
Recorded changes49 · last 18 Sep 2026derived

Affected & Fixed Versions as published

Affected productMicrosoft Windows Server 2008 R2 Service Pack 1; Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation); Microsoft Windows Server 2008 Service Pack 2…receipt
Published rangesmicrosoft windows server 2004 < 10.0.19041.1348; microsoft windows server 2008 r2; microsoft windows server 2012 r2; microsoft windows server 2016 < 10.0.14393.4770receipt
Show all 7 published ranges
microsoft windows server 2004 < 10.0.19041.1348
microsoft windows server 2008 r2
microsoft windows server 2012 r2
microsoft windows server 2016 < 10.0.14393.4770
microsoft windows server 2019 < 10.0.17763.2300
microsoft windows server 2022 < 10.0.20348.350
microsoft windows server 20h2 < 10.0.19042.1348
Fixed in6.1.7601.25769; 6.0.6003.21282; 6.2.9200.23517; 6.3.9600.20174; 10.0.14393.4770; 10.0.17763.2300; 10.0.20348.350; 10.0.19041.1348; 10.0.19042.1348receipt

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

Active Directory Domain Services Elevation of Privilege Vulnerability receipt

NVD's analysis a second authority

severity
6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P
affected versions
microsoft windows server 2004 < 10.0.19041.1348; microsoft windows server 2008 r2; microsoft windows server 2012 r2; and 4 more, listed in full below
also scored by
[email protected] 7.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H · [email protected] 7.5 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

The CNA scored it 7.5 and NVD 6.5. Both are shown because both were published; we do not pick one.

check it yourself msrc.microsoft.com receipt

Dated events

2021-12-12EPSS moved 0.05 to 0.182022-04-11Added to CISA KEV2022-05-02CISA remediation due2023-03-07EPSS moved 0.02 to 0.972026-06-15EPSS moved 0.94 to 0.70

Movement the material steps

10 Nov 20210.00416
12 Dec 20210.17642 · crossed 0.10
4 Feb 20220.02288 · crossed 0.10
7 Mar 20230.97166 · crossed 0.10 and 0.50 and 0.90 · scoring model v2023.03.01
29 Dec 20230.70002 · crossed 0.90
1 Feb 20240.59906
4 Jul 20240.00630 · crossed 0.10 and 0.50
17 Mar 20250.94074 · crossed 0.10 and 0.50 and 0.90 · scoring model v2025.03.14
15 Jun 20260.70207 · crossed 0.90 · scoring model v2026.06.15
3 Sep 20260.73297

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

Show all 35 observations
10 Nov 20210.00416
13 Nov 20210.04557
12 Dec 20210.17642
4 Feb 20220.02288
7 Mar 20230.97166
13 Mar 20230.97132
26 Mar 20230.96756
9 Apr 20230.96635
8 May 20230.96553
2 Jun 20230.96357
1 Jul 20230.95674
8 Jul 20230.95530
29 Aug 20230.94655
26 Sep 20230.94366
9 Oct 20230.92613
23 Nov 20230.92808
6 Dec 20230.92466
29 Dec 20230.70002
1 Feb 20240.59906
8 May 20240.58500
4 Jul 20240.00630
9 Aug 20240.00747
21 Aug 20240.00630
2 Oct 20240.00891
16 Oct 20240.00737
17 Dec 20240.00658
27 Dec 20240.00567
17 Mar 20250.94074
15 Apr 20250.94019
31 Oct 20250.94066
18 Nov 20250.9355
21 Nov 20250.94066
15 Jun 20260.70207
20 Aug 20260.72027
3 Sep 20260.73297

35 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 0.73297Published2021-11-10Public PoC2021-12-11CISA KEV2022-04-11Index as of2026-09-04

Listed by CISA 152 days after it published, exploit probability more than doubled between 2021-11-10 and 2021-11-13 (0.00416 → 0.04557) and the record had been public for 4 years, 9 months when this index was last written.

Published 2021-11-10 receipt · Public PoC 2021-12-11 receipt · CISA KEV 2022-04-11 receipt · Index as of 2026-09-04 derived

Siblings and hubs

Records related to this one

Its defect family

microsoft windows server 2008 r2 service pack 1

Of the 2 records in this family, this is the only one with public proof-of-concept code, and it holds 6 references to it.

Grouped by shared product and weakness, not by shared vulnerability. Each record's own state is on its own page.

Family membership: held values

This record is one of a group, and the group's page describes all of them. This page is kept and dated, and the defect family's own page is the one we offer for indexing: the whole group.

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What usually comes next

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