CASCACascade Atlas

Evidence dossier

CVE-2021-21206

Use after free in Blink in Google Chrome prior to 89.0.4389.128 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 9.4% exploit likelihood as of Aug 27, 2026.

72.3–73.4Priority 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 89.0.4389.128 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

State
PUBLISHED
Published
Apr 26, 2021
Updated
Oct 21, 2025
Evidence coverage
97%

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 89.0.4389.128 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 89.0.4389.128 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: 9.4% probability · 95.04th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.094010000000; percentile 0.950360000000
    Original evidence ↗
ExploitationCatalog member

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

Exploit likelihood9.40%

FIRST EPSS · score date Aug 27, 2026 · 95th 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 89.0.4389.128 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 89.0.4389.128 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

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

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

9.4% probability · 95.04th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.094010000000; percentile 0.950360000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
4Underlying assertions
2Canonical products
4Target assertions
0Constraint assertions

Grouped from 2 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

3 scope groups

Chrome · source assertedGoogleChromeDirect source scope
Affected: unspecified to before 89.0.4389.128 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "unspecified", "lessThan": "89.0.4389.128", "versionType": "custom"}]
NVD CPE · OPERATING SYSTEMfedoraprojectfedoraVulnerable target · 3 assertions
Version 32; Version 33; Version 34Canonical identity product-c96c7662a6606ed7594747da3d7ba9ee3a9758ab11658f6a3f42616361472e47Linked exact
Scope supported
Inspect raw assertions
  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
  2. cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 2
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    a930e247-0b43-43cb-98ff-6ce7b8189835
  3. cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    e460aa51-fcda-46b9-ae97-e6676aa5e194
NVD CPE · APPLICATIONgooglechromeVulnerable target · 1 assertions
Any version (unconstrained) (< 89.0.4389.128)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 89.0.4389.128
    Match ID
    060c60a1-9a64-4b1d-a546-8397599de453

Affected-product evidence

Accepted scope and product mapping

2 canonical links · 1 source-reported links

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
8efca09a-9afe-4656-881b-d98596fe2874
Mapping establishedEvidence supported

vendor-2d566b06907460b10e6e48c8544126e19f1d6df137983056edae8d0b51e34e45 · product-c96c7662a6606ed7594747da3d7ba9ee3a9758ab11658f6a3f42616361472e47

Source class
Nvd cpe vulnerable target
Assertions
3
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
2253d351-dc95-400a-bb2b-7b992caba4483b14c7f5-c930-4877-af9f-36e4db8a4852a52d7ca1-9ec5-4536-ad85-0a987f51816b
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
7010cc80-e6e2-4ac3-9d8b-dff59ed3da8c

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.