CASCACascade Atlas

Evidence dossier

CVE-2021-28550

Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution

Exploited in the wild (CISA KEV since Nov 3, 2021). NVD reports CVSS 3.1 8.8. EPSS estimates 52.0% exploit likelihood as of Aug 26, 2026.

81.0–82.1Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.001.30020 (and earlier) and 2017.011.30194 (and earlier) are affected by a Use After Free vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

State
PUBLISHED
Published
Sep 2, 2021
Updated
Oct 21, 2025
Evidence coverage
98%

Evidence chronology

What was known when

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

    Record text: Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution

    Inspect raw assertion
    Field
    container
    Value
    Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution
    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: Adobe Acrobat and Reader Use-After-Free Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Adobe Acrobat and Reader Use-After-Free Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 52.01% probability · 98.87th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.520050000000; percentile 0.988680000000
    Original evidence ↗
ExploitationCatalog member

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

Exploit likelihood52.01%

FIRST EPSS · score date Aug 26, 2026 · 98.9th percentile · first observed Aug 26, 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

adobeOriginal assertion
Record text

Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution

Inspect raw assertion
Field
container
Value
Adobe Acrobat Reader use after free vulnerability could lead to arbitrary code execution
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

Adobe Acrobat and Reader Use-After-Free Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Adobe Acrobat and Reader Use-After-Free Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

52.01% probability · 98.87th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.520050000000; percentile 0.988680000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
12Underlying assertions
6Canonical products
8Target assertions
4Constraint assertions

Grouped from 6 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

7 scope groups

adobe · source assertedAdobeAcrobat ReaderDirect source scope
Affected: unspecified through 2020.001.30020 (custom comparison)Affected: unspecified through 2021.001.20150 (custom comparison)Affected: unspecified through 2017.011.30194 (custom comparison)Affected: unspecified through None (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "unspecified", "versionType": "custom", "lessThanOrEqual": "2020.001.30020"}, {"status": "affected", "version": "unspecified", "versionType": "custom", "lessThanOrEqual": "2021.001.20150"}, {"status": "affected", "version": "unspecified", "versionType": "custom", "lessThanOrEqual": "2017.011.30194"}, {"status": "affected", "version": "unspecified", "versionType": "custom", "lessThanOrEqual": "None"}]
NVD CPE · APPLICATIONadobeacrobatVulnerable target · 2 assertions
Any version (unconstrained) (>= 17.011.30059, <= 17.011.30194); Any version (unconstrained) (>= 20.001.30005, <= 20.001.30020)Canonical identity product-ed5d44367bdcb90bad355d7e7359a851dedc6267deefc08f1c50b65634b9019cLinked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 0
    Logic
    OR
    Version bounds
    from including 17.011.30059; through including 17.011.30194
    Match ID
    072ab504-dcfa-4d7f-a1a6-c7dd723b7c8d
  2. cpe:2.3:a:adobe:acrobat:*:*:*:*:classic:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 1
    Logic
    OR
    Version bounds
    from including 20.001.30005; through including 20.001.30020
    Match ID
    aeda8877-0fef-4f2f-b200-fa556ca0374b
NVD CPE · APPLICATIONadobeacrobat_dcVulnerable target · 2 assertions
Any version (unconstrained) (>= 15.008.20082, <= 21.001.20149); Any version (unconstrained) (>= 15.008.20082, <= 21.001.20150)Canonical identity product-d52f4403db2ec33efef1ee4992d557c81863172cde027cc48feadace7f308abeLinked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    from including 15.008.20082; through including 21.001.20150
    Match ID
    1293ebdc-700e-4c44-af0c-c16f4d790a62
  2. cpe:2.3:a:adobe:acrobat_dc:*:*:*:*:continuous:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    2 · node/0 · match 0
    Logic
    OR
    Version bounds
    from including 15.008.20082; through including 21.001.20149
    Match ID
    20af30d7-d943-4971-bec1-5b2623cb9bd4
NVD CPE · APPLICATIONadobeacrobat_readerVulnerable target · 2 assertions
Any version (unconstrained) (>= 17.011.30059, <= 17.011.30194); Any version (unconstrained) (>= 20.001.30005, <= 20.001.30020)Canonical identity product-600b6c3e0d80d39770793f8a9da27b869cd246427b21a98d939c2f7b40e67886Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 3
    Logic
    OR
    Version bounds
    from including 20.001.30005; through including 20.001.30020
    Match ID
    77cc3021-6ed3-48e1-a81e-34a9d33bd8d3
  2. cpe:2.3:a:adobe:acrobat_reader:*:*:*:*:classic:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    1 · node/0 · match 2
    Logic
    OR
    Version bounds
    from including 17.011.30059; through including 17.011.30194
    Match ID
    ca2983ec-06f6-4970-8ece-18c21cb5db60
NVD CPE · APPLICATIONadobeacrobat_reader_dcVulnerable target · 2 assertions
Any version (unconstrained) (>= 15.008.20082, <= 21.001.20149); Any version (unconstrained) (>= 15.008.20082, <= 21.001.20150)Canonical identity product-555cc538304e4c7c06c06beb18e8ee52245d2f3acee3e0665299abb4e555a3d9Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    2 · node/0 · match 1
    Logic
    OR
    Version bounds
    from including 15.008.20082; through including 21.001.20149
    Match ID
    d1968413-69fa-43d2-9776-ff98958d1402
  2. cpe:2.3:a:adobe:acrobat_reader_dc:*:*:*:*:continuous:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    from including 15.008.20082; through including 21.001.20150
    Match ID
    781005a7-8966-40b5-a8c1-d767a5cbda0d
NVD CPE · OPERATING SYSTEMapplemacosEnvironmental constraint · 2 assertions
Version not applicableCanonical identity product-d6f53ba981bb58ea2b0d24855b8ff4a18555e3a17a9dce0d38460a69537bbc63Linked exact
Scope constrained
Inspect raw assertions
  1. cpe:2.3:o:apple:macos:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    1 · node/1 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    387021a0-af36-463c-a605-32ea7dac172e
  2. cpe:2.3:o:apple:macos:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    2 · node/1 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    387021a0-af36-463c-a605-32ea7dac172e
NVD CPE · OPERATING SYSTEMmicrosoftwindowsEnvironmental constraint · 2 assertions
Version not applicableCanonical identity product-6a798dc931affc038ba266631a506d54b455ffebd96b4fae68f77b6bd7aef178Linked exact
Scope constrained
Inspect raw assertions
  1. cpe:2.3:o:microsoft:windows:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    1 · node/1 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    a2572d17-1de6-457b-99cc-64afd54487ea
  2. cpe:2.3:o:microsoft:windows:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    a2572d17-1de6-457b-99cc-64afd54487ea

Affected-product evidence

Accepted scope and product mapping

4 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-70d8e9d1eb9ce5b2e6b4c9351aebc88bced6ea77611cbc8d5cdbe8115b6faed8 · product-555cc538304e4c7c06c06beb18e8ee52245d2f3acee3e0665299abb4e555a3d9

Source class
Nvd cpe vulnerable target
Assertions
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
3ca5353a-c9ee-46c0-9eb5-7ec67efe31708a718c85-fdc5-453e-9d70-cdcb03cd54c1
Mapping establishedEvidence supported

vendor-70d8e9d1eb9ce5b2e6b4c9351aebc88bced6ea77611cbc8d5cdbe8115b6faed8 · product-600b6c3e0d80d39770793f8a9da27b869cd246427b21a98d939c2f7b40e67886

Source class
Nvd cpe vulnerable target
Assertions
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
226679ce-5cc6-4e04-8cbb-157ccad3883978b6fc31-478d-4caf-85ca-0a8e2212bc83
Mapping establishedEvidence supported

vendor-70d8e9d1eb9ce5b2e6b4c9351aebc88bced6ea77611cbc8d5cdbe8115b6faed8 · product-d52f4403db2ec33efef1ee4992d557c81863172cde027cc48feadace7f308abe

Source class
Nvd cpe vulnerable target
Assertions
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
4e0e65a2-1dda-4e2f-beca-8c27397b2aa55e3e75a3-fb1b-442c-aa89-19df5d43588d
Mapping establishedEvidence supported

vendor-70d8e9d1eb9ce5b2e6b4c9351aebc88bced6ea77611cbc8d5cdbe8115b6faed8 · product-ed5d44367bdcb90bad355d7e7359a851dedc6267deefc08f1c50b65634b9019c

Source class
Nvd cpe vulnerable target
Assertions
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
46f46e87-9cd0-4125-95f2-06f19fc97282b2efcf5b-5d7d-434e-9001-d265a4a5961c
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
32cf8b29-5cd1-4d86-b0f9-3543154345dc

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
9.6
psirt@adobe.comCVSS 3.0 · role Secondary · priority eligiblevalid_matchCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
9.6
adobeCVSS 3.0 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Direct CVE/CNA normalized decisions

9.6Priority eligible

adobe

CVSS 3.0 · Primary · Original assertion · rank 1

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Validation
Valid match
Recomputed
9.6
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.