CASCACascade Atlas

Evidence dossier

CVE-2026-81963

Windows Update Stack Elevation of Privilege Vulnerability

Exploited in the wild (CISA KEV since Sep 8, 2026). microsoft reports CVSS 3.1 7.8. EPSS estimates 0.4% exploit likelihood as of Oct 22, 2026.

60.8–71.5Priority evidence range
Evidence through Oct 22, 2026, 6:07 PM UTC

As of Oct 22, 2026

Normalized restatement

Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.

State
PUBLISHED
Published
Sep 8, 2026
Updated
Oct 14, 2026
Evidence coverage
85%

Evidence chronology

What was known when

Download this view's receipt →
  1. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: Microsoft Windows Link Following Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Microsoft Windows Link Following Vulnerability
    Original evidence ↗
  2. Source dateSource date omittedFirst observed by CASCA
    CISA-ADP

    Record text: CISA ADP Vulnrichment

    Inspect raw assertion
    Field
    container
    Value
    CISA ADP Vulnrichment
    Original evidence ↗
  3. Source dateSource date omittedFirst observed by CASCA
    microsoft

    Record text: Windows Update Stack Elevation of Privilege Vulnerability

    Inspect raw assertion
    Field
    container
    Value
    Windows Update Stack Elevation of Privilege Vulnerability
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 0.39% probability · 32.34th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.003930000000; percentile 0.323430000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Sep 8, 2026 · first observed Sep 8, 2026

Exploit likelihood0.39%

FIRST EPSS · score date Oct 22, 2026 · 32.3th percentile · first observed Oct 22, 2026

SeverityCVSS 7.8

microsoft · CVSS 3.1 · first observed Oct 15, 2026 · same-version scores align in this snapshot

Evidence detail

Source limits and decisions

Why each evidence state has this value

casca-unknown-reasons-v1
Exploitation statusLast verified source snapshot retained

The last verified source boundary remains in force for this claim.

Revision
evidence-policy-v1.1.0
Cutoff
Oct 22, 2026
Resolution
Review source contract
Exploit likelihoodEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Oct 22, 2026
Resolution
None
Severity assessmentEvidence supported

Eligible evidence is present for this bounded claim.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Oct 22, 2026
Resolution
None
Affected productsSource-reported scope

The cited source assertion is retained while canonical product linkage remains open.

Revision
casca-factor-d-obligations-v1
Cutoff
Oct 22, 2026
Resolution
Resolve identity

Source comparison

Who said what

CISA KEVOriginal assertion
Exploitation cataloged

Microsoft Windows Link Following Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Microsoft Windows Link Following Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
CISA-ADPIndependent enrichment
Record text

CISA ADP Vulnrichment

Inspect raw assertion
Field
container
Value
CISA ADP Vulnrichment
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
microsoftOriginal assertion
Record text

Windows Update Stack Elevation of Privilege Vulnerability

Inspect raw assertion
Field
container
Value
Windows Update Stack Elevation of Privilege Vulnerability
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

0.39% probability · 32.34th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.003930000000; percentile 0.323430000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →

16 scope groups

microsoft · source assertedMicrosoftWindows 11 version 23H2Direct source scope
Affected: 10.0.22631.0 to before 10.0.22631.7582 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.22631.0", "lessThan": "10.0.22631.7582", "versionType": "custom"}]
microsoft · source assertedMicrosoftWindows 11 Version 23H2Direct source scope
Affected: 10.0.22631.0 to before 10.0.22631.7582 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.22631.0", "lessThan": "10.0.22631.7582", "versionType": "custom"}]
microsoft · source assertedMicrosoftWindows 11 Version 24H2Direct source scope
Affected: 10.0.26100.0 to before 10.0.26100.9445 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.26100.0", "lessThan": "10.0.26100.9445", "versionType": "custom"}]
microsoft · source assertedMicrosoftWindows 11 Version 25H2Direct source scope
Affected: 10.0.26200.0 to before 10.0.26200.9445 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.26200.0", "lessThan": "10.0.26200.9445", "versionType": "custom"}]
microsoft · source assertedMicrosoftWindows 11 version 26H1Direct source scope
Affected: 10.0.28000.0 to before 10.0.28000.2954 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.28000.0", "lessThan": "10.0.28000.2954", "versionType": "custom"}]
microsoft · source assertedMicrosoftWindows Server 2025Direct source scope
Affected: 10.0.26100.0 to before 10.0.26100.33438 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.26100.0", "lessThan": "10.0.26100.33438", "versionType": "custom"}]
microsoft · source assertedMicrosoftWindows Server 2025 (Server Core installation)Direct source scope
Affected: 10.0.26100.0 to before 10.0.26100.33438 (custom comparison)
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "10.0.26100.0", "lessThan": "10.0.26100.33438", "versionType": "custom"}]
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*; end excluding 10.0.22631.7582
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*; end excluding 10.0.22631.7582
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*; end excluding 10.0.26100.9445
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*; end excluding 10.0.26100.9445
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*; end excluding 10.0.26200.9445
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*; end excluding 10.0.26200.9445
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:arm64:*; end excluding 10.0.28000.2954
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:x64:*; end excluding 10.0.28000.2954
NVD · source assertedVendor unspecified by sourceProduct unspecified by sourceDirect source scope
Version bounds not stated
Scope supported
Inspect raw assertioncpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*; end excluding 10.0.26100.33438

Affected-product evidence

Accepted scope and product mapping

0 canonical links · 2 source-reported links

Source-reported scopeSource-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Vendor specified only by source · Product specified only by source

Source class
Direct cve affected
Assertions
7
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Oct 22, 2026
Retained assertion IDs
265a25e4-4567-419f-97fd-1d81c3e1d21581bb9ba5-e681-48be-b0a2-3bbbaca5cc6c8a69323c-afb3-42e2-a55b-a30b5cd572d8c3c16c09-0ecf-4eed-a4c5-b0def69efe3ec70e8f62-c934-46fd-960e-7a5759ee4dcbcf68b618-a61d-441c-a1f4-7056b43dbac6dc89f6cd-b7e2-4612-8d87-c7b6c6348e6c
Source-reported scopeSource-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Vendor specified only by source · Product specified only by source

Source class
Nvd cpe vulnerable target
Assertions
9
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Oct 22, 2026
Retained assertion IDs
0ec8a5f8-a8ed-4b92-bb02-b667140f706c1783186f-46c2-4ed1-94d5-244df26877e41996ae5f-f776-4667-a25d-c830e6ca2c8a3db4c8d6-f489-4abc-9b56-512f765d48ce5b67421a-4e53-433f-af82-2dc9e99149ffaefcaf98-a61b-4e33-9799-e24310dd2d70b545df45-a015-4e23-8765-f841a1095f32c46a7eab-3355-4459-8ca4-299c2cfc6f22cca644f9-8066-4017-83ba-ce6df55fa687

Assessments

CVSS by origin

7.8
secure@microsoft.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8
microsoftCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

Direct CVE/CNA normalized decisions

7.8Priority eligible

microsoft

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Validation
Valid match
Recomputed
7.8
Decision reason
Evidence supported
Policy
casca-direct-cvss-eligibility-v1

Assessments are retained side by side under closed precedence. Cascade never averages CVSS.

Evidence boundaries

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; remaining scope stays source-scoped.
  • NVD-carried upstream facts remain derivative; independent corroboration requires a separately authored source.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.
  • OSV aggregation and OSV-converted NVD material are not independent corroboration.
  • Red Hat facts are vendor assertions for the exact supplied products.
  • Nonmembership and not-yet-observed states are not proof of safety.