CASCACascade Atlas

Evidence dossier

CVE-2026-20963

Microsoft SharePoint Remote Code Execution Vulnerability

Exploited in the wild (CISA KEV since Mar 18, 2026). microsoft reports CVSS 3.1 9.8. EPSS estimates 31.6% exploit likelihood as of Aug 27, 2026.

78.4–81.9Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.

State
PUBLISHED
Published
Jan 13, 2026
Updated
Jul 30, 2026
Evidence coverage
92%

Evidence chronology

What was known when

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

    Exploitation cataloged: Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Microsoft SharePoint Deserialization of Untrusted Data 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: Microsoft SharePoint Remote Code Execution Vulnerability

    Inspect raw assertion
    Field
    container
    Value
    Microsoft SharePoint Remote Code Execution Vulnerability
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 31.55% probability · 98.15th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.315540000000; percentile 0.981530000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Mar 18, 2026 · first observed Jul 19, 2026

Exploit likelihood31.55%

FIRST EPSS · score date Aug 27, 2026 · 98.2th percentile · first observed Aug 27, 2026

SeverityCVSS 9.8

microsoft · CVSS 3.1 · first observed Aug 1, 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 statusEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Aug 27, 2026
Resolution
None
Exploit likelihoodEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Aug 27, 2026
Resolution
None
Severity assessmentEvidence supported

Eligible evidence is present for this bounded claim.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Aug 27, 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
Aug 27, 2026
Resolution
Resolve identity

Source comparison

Who said what

CISA KEVOriginal assertion
Exploitation cataloged

Microsoft SharePoint Deserialization of Untrusted Data Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Microsoft SharePoint Deserialization of Untrusted Data 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

Microsoft SharePoint Remote Code Execution Vulnerability

Inspect raw assertion
Field
container
Value
Microsoft SharePoint Remote Code Execution Vulnerability
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

31.55% probability · 98.15th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.315540000000; percentile 0.981530000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
3Underlying assertions
1Canonical products
3Target assertions
0Constraint assertions

Grouped from 1 configuration nodes in this exact snapshot. Visual grouping is navigational; asset exposure and root cause require cited evidence.

Identity source boundaries
  • Cpe dictionary1,775,266 records · observed through 2026-07-21T06:45:29.809Z27d65b0f-b718-4b4f-bb79-c47c68d09dfa
  • Cpe match643,502 records · observed through 2026-07-21T08:13:17.697Z955dae73-7302-438b-aee1-058d7cc5d48e

4 scope groups

microsoft · source assertedMicrosoftMicrosoft SharePoint Enterprise Server 2016Direct source scope
Affected: 16.0.0 to before 16.0.5535.1001 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "16.0.0", "lessThan": "16.0.5535.1001", "versionType": "custom"}]
microsoft · source assertedMicrosoftMicrosoft SharePoint Server 2019Direct source scope
Affected: 16.0.0 to before 16.0.10417.20083 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "16.0.0", "lessThan": "16.0.10417.20083", "versionType": "custom"}]
microsoft · source assertedMicrosoftMicrosoft SharePoint Server Subscription EditionDirect source scope
Affected: 16.0.0 to before 16.0.19127.20442 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "16.0.0", "lessThan": "16.0.19127.20442", "versionType": "custom"}]
NVD CPE · APPLICATIONmicrosoftsharepoint_serverVulnerable target · 3 assertions
Any version (unconstrained) (< 16.0.19127.20442); Version 2016; Version 2019Canonical identity product-77f9def9702aa8ece74aa62c4de32bc72b167cb6f10f2eff44492cf46afc2e03Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    6122d014-5bf1-4af4-8b4d-80205ed7785e
  2. cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    f815ef1d-7b60-47be-9ac2-2548f99f10e4
  3. cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    through excluding 16.0.19127.20442
    Match ID
    fb9eca81-c1e2-4b02-a45c-0e5664e3c9b9

Affected-product evidence

Accepted scope and product mapping

1 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-01299a5a765aea70faa05f2d06e0c26a5d498fd34553e868d89e8a43b31864db · product-77f9def9702aa8ece74aa62c4de32bc72b167cb6f10f2eff44492cf46afc2e03

Source class
Nvd cpe vulnerable target
Assertions
3
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
4b7d993b-43b9-4a72-9b8a-9e5869365bbd9f6e9d51-bf6e-4410-a0bc-9eb5cfcff910f97b1048-fb04-4a43-997d-c5660f918982
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
3
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
558b1156-03de-4fe7-92b9-b56b1c81badc71c75ae7-8802-4df9-9979-17206641647bd57d2c6c-d86a-4c7b-ba03-0a56c12ece77

Assessments

CVSS by origin

9.8
secure@microsoft.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8
microsoftCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Direct CVE/CNA normalized decisions

9.8Priority eligible

microsoft

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Validation
Valid match
Recomputed
9.8
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.