CASCACascade Atlas

Evidence dossier

CVE-2021-21193

Use after free in Blink in Google Chrome prior to 89.0.4389.90 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

Exploited in the wild (CISA KEV since Nov 3, 2021). NVD reports CVSS 3.1 8.8. EPSS estimates 9.9% exploit likelihood as of Aug 27, 2026.

73.6–74.4Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

Use after free in Blink in Google Chrome prior to 89.0.4389.90 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

State
PUBLISHED
Published
Mar 16, 2021
Updated
Oct 21, 2025
Evidence coverage
96%

Evidence chronology

What was known when

Download this view's receipt →
  1. Source dateSource date omittedFirst observed by CASCA
    Chrome

    Record text: Use after free in Blink in Google Chrome prior to 89.0.4389.90 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

    Inspect raw assertion
    Field
    container
    Value
    Use after free in Blink in Google Chrome prior to 89.0.4389.90 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
    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: Google Chromium Blink Use-After-Free Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Google Chromium Blink Use-After-Free Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 9.87% probability · 95.21th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.098700000000; percentile 0.952070000000
    Original evidence ↗
ExploitationCatalog member

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

Exploit likelihood9.87%

FIRST EPSS · score date Aug 27, 2026 · 95.2th percentile · first observed Aug 27, 2026

SeverityCVSS 8.8

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

ChromeOriginal assertion
Record text

Use after free in Blink in Google Chrome prior to 89.0.4389.90 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

Inspect raw assertion
Field
container
Value
Use after free in Blink in Google Chrome prior to 89.0.4389.90 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA-ADPIndependent enrichment
Record text

CISA ADP Vulnrichment

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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

Google Chromium Blink Use-After-Free Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Google Chromium Blink Use-After-Free Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

9.87% probability · 95.21th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.098700000000; percentile 0.952070000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
3Underlying assertions
3Canonical products
3Target 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

4 scope groups

Chrome · source assertedGoogleChromeDirect source scope
Affected: unspecified to before 89.0.4389.90 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "unspecified", "lessThan": "89.0.4389.90", "versionType": "custom"}]
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
    2 · 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 32Canonical identity product-c96c7662a6606ed7594747da3d7ba9ee3a9758ab11658f6a3f42616361472e47Linked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    36d96259-24bd-44e2-96d9-78ce1d41f956
NVD CPE · APPLICATIONgooglechromeVulnerable target · 1 assertions
Any version (unconstrained) (< 89.0.4389.90)Canonical identity product-6239ec405e2e1cdd75fd8ed01bb6845a448ecca3c3edcc8b0c5ccc2adb8b6bcdLinked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:a:google:chrome:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    through excluding 89.0.4389.90
    Match ID
    66251c61-17b9-4437-b3d7-75a75bcce0fd

Affected-product evidence

Accepted scope and product mapping

3 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
4ed93486-1ae5-45ba-9b26-e0e229dabb81
Mapping establishedEvidence supported

vendor-88869ec57256fdf5d0b9ffd6f3d141ad371acdd6f81405ddb6c5e9e45b10869c · product-6239ec405e2e1cdd75fd8ed01bb6845a448ecca3c3edcc8b0c5ccc2adb8b6bcd

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
c5b5fb3f-29d5-467d-b920-bb977e4a6008
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
a15338b0-50c5-4810-914e-e8a7d11a5131
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
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
2e8563fd-a1ce-4057-9d93-6f2025ec81f1

Assessments

CVSS by origin

8.8
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8
NVDCVSS 2.0 · role Primary · priority eligiblevalid_matchAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8
CVE Program sourceCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8
CISA-ADPCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Direct CVE/CNA normalized decisions

8.8Priority eligible

CISA-ADP

CVSS 3.1 · Secondary · Independent enrichment · rank 2

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Validation
Valid match
Recomputed
8.8
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.