CASCACascade Atlas

Evidence dossier

CVE-2021-1871

A logic issue was addressed with improved restrictions.

Exploited in the wild (CISA KEV since Nov 3, 2021). NVD reports CVSS 3.1 9.8. EPSS estimates 7.0% exploit likelihood as of Aug 27, 2026.

76.3–77.5Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

State
PUBLISHED
Published
Apr 2, 2021
Updated
Oct 21, 2025
Evidence coverage
97%

Evidence chronology

What was known when

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  1. Source dateSource date omittedFirst observed by CASCA
    apple

    Record text: A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

    Inspect raw assertion
    Field
    container
    Value
    A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
    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
    CVE Program

    Record text: CVE Program Container

    Inspect raw assertion
    Field
    container
    Value
    CVE Program Container
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 7% probability · 93.68th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.070020000000; percentile 0.936800000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Nov 3, 2021 · first observed Jul 19, 2026

Exploit likelihood7.00%

FIRST EPSS · score date Aug 27, 2026 · 93.7th percentile · first observed Aug 27, 2026

SeverityCVSS 9.8

NVD · CVSS 3.1 · first observed Jul 19, 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

appleOriginal assertion
Record text

A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

Inspect raw assertion
Field
container
Value
A logic issue was addressed with improved restrictions. This issue is fixed in macOS Big Sur 11.2, Security Update 2021-001 Catalina, Security Update 2021-001 Mojave, iOS 14.4 and iPadOS 14.4. A remote attacker may be able to cause arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
Source dateSource date omittedFirst 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 ↗
CVE ProgramDerivative copy
Record text

CVE Program Container

Inspect raw assertion
Field
container
Value
CVE Program Container
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

7% probability · 93.68th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.070020000000; percentile 0.936800000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
9Underlying assertions
6Canonical products
9Target assertions
0Constraint assertions

Grouped from 3 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

8 scope groups

apple · source assertedAppleiOS and iPadOSDirect source scope
Affected: unspecified to before 14.4 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "unspecified", "lessThan": "14.4", "versionType": "custom"}]
apple · source assertedApplemacOSDirect source scope
Affected: unspecified to before 11.2 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "unspecified", "lessThan": "11.2", "versionType": "custom"}]
NVD CPE · OPERATING SYSTEMappleipadosVulnerable target · 1 assertions
Any version (unconstrained) (< 14.4)Canonical identity product-8e7094ac066248cd4828b6ec8e3a96d010ed1c68f6083af46638775d737da0adLinked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:apple:ipados:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    through excluding 14.4
    Match ID
    17aaea98-4c05-496e-81a7-ac031fcddda5
NVD CPE · OPERATING SYSTEMappleiphone_osVulnerable target · 1 assertions
Any version (unconstrained) (< 14.4)Canonical identity product-665d7155d02581979844685e7fca6c2680af997f9200af455887b1c71c483272Linked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:apple:iphone_os:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    through excluding 14.4
    Match ID
    062166d7-2444-4022-b7e4-13884c43edca
NVD CPE · OPERATING SYSTEMapplemacosVulnerable target · 1 assertions
Any version (unconstrained) (>= 11.0.1, < 11.2)Canonical identity product-d6f53ba981bb58ea2b0d24855b8ff4a18555e3a17a9dce0d38460a69537bbc63Linked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 6
    Logic
    OR
    Version bounds
    from including 11.0.1; through excluding 11.2
    Match ID
    084f8722-a895-4fc2-821e-df0b129653bc
NVD CPE · OPERATING SYSTEMapplemac_os_xVulnerable target · 4 assertions
Any version (unconstrained) (>= 10.15, < 10.15.7); Version 10.15.7Canonical identity product-94613e1f5039e71a9805f20421d56ac6a61e2707d3f97a08fdf6823a65dc7b76Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:o:apple:mac_os_x:10.15.7:supplemental_update:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 5
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    c1c795b9-e58d-467c-83a8-2d45c792292f
  2. cpe:2.3:o:apple:mac_os_x:10.15.7:-:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 3
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    a654b8a2-fc30-4171-b0bb-366cd7ed4b6a
  3. cpe:2.3:o:apple:mac_os_x:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    from including 10.15; through excluding 10.15.7
    Match ID
    db8a73f8-3074-4b32-b9f6-343b6b1988c5
  4. cpe:2.3:o:apple:mac_os_x:10.15.7:security_update_2020:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 4
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    f12cc8b5-c1eb-419e-8496-b9a3864656ad
NVD CPE · OPERATING SYSTEMdebiandebian_linuxVulnerable target · 1 assertions
Version 10.0Canonical identity product-3ccb4bc87dfae98fa2f2a06435fe5b3d9be78572fb958a89f2d7a96b4066447eLinked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    07b237a9-69a3-4a9c-9da0-4e06bd37ae73
NVD CPE · OPERATING SYSTEMfedoraprojectfedoraVulnerable target · 1 assertions
Version 33Canonical identity product-c96c7662a6606ed7594747da3d7ba9ee3a9758ab11658f6a3f42616361472e47Linked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    2 · node/0 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    e460aa51-fcda-46b9-ae97-e6676aa5e194

Affected-product evidence

Accepted scope and product mapping

6 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-66ae8c5e06427f7450637d18322b0dc411c0b469d940341cf076a620d444fe3c · product-3ccb4bc87dfae98fa2f2a06435fe5b3d9be78572fb958a89f2d7a96b4066447e

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
e02e9232-b3e1-42e8-af1f-d326ce34b924
Mapping establishedEvidence supported

vendor-d6ed6f1e35de2e16a8a10f2ae364dab009bb2afadd609071b20da24d60ce2829 · product-665d7155d02581979844685e7fca6c2680af997f9200af455887b1c71c483272

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
923e117b-1846-49ed-888a-4e889846296f
Mapping establishedEvidence supported

vendor-d6ed6f1e35de2e16a8a10f2ae364dab009bb2afadd609071b20da24d60ce2829 · product-8e7094ac066248cd4828b6ec8e3a96d010ed1c68f6083af46638775d737da0ad

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
52ec3818-d111-4c70-bae4-a193ba2d6a45
Mapping establishedEvidence supported

vendor-d6ed6f1e35de2e16a8a10f2ae364dab009bb2afadd609071b20da24d60ce2829 · product-94613e1f5039e71a9805f20421d56ac6a61e2707d3f97a08fdf6823a65dc7b76

Source class
Nvd cpe vulnerable target
Assertions
4
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
40c3be62-12ff-4af4-8f6a-54ee5212d27873aa7ced-6d03-48fe-8138-7f4ef03f2f2c897ee2ce-d68d-40ae-a266-4c49c7bcda56fe8c3016-00b4-445d-b49e-cc3aa516d682
Mapping establishedEvidence supported

vendor-2d566b06907460b10e6e48c8544126e19f1d6df137983056edae8d0b51e34e45 · product-c96c7662a6606ed7594747da3d7ba9ee3a9758ab11658f6a3f42616361472e47

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
92c577c0-e655-4c46-825b-509e85250aa6
Mapping establishedEvidence supported

vendor-d6ed6f1e35de2e16a8a10f2ae364dab009bb2afadd609071b20da24d60ce2829 · product-d6f53ba981bb58ea2b0d24855b8ff4a18555e3a17a9dce0d38460a69537bbc63

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
a1907669-8671-4a2a-b104-48a3ac285545
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
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
c97c23d9-af1e-4f52-90e6-241477c8b77cce2292ac-4519-49c9-8771-4c907164dc3b

Assessments

CVSS by origin

9.8
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5
NVDCVSS 2.0 · role Primary · priority eligiblevalid_matchAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8
CVE Program sourceCVSS 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
CISA-ADPCVSS 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

Direct CVE/CNA normalized decisions

9.8Priority eligible

CISA-ADP

CVSS 3.1 · Secondary · Independent enrichment · rank 2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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.