CASCACascade Atlas

Evidence dossier

CVE-2025-53521

BigIP APM Vulnerability

Exploited in the wild (CISA KEV since Mar 27, 2026). f5 reports CVSS 4.0 9.3. EPSS estimates 2.2% exploit likelihood as of Aug 27, 2026.

68.9–70.4Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

State
PUBLISHED
Published
Oct 15, 2025
Updated
Mar 31, 2026
Evidence coverage
97%

Evidence chronology

What was known when

Download this view's receipt →
  1. 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 ↗
  2. Source dateSource date omittedFirst observed by CASCA
    f5

    Record text: BigIP APM Vulnerability

    Inspect raw assertion
    Field
    container
    Value
    BigIP APM Vulnerability
    Original evidence ↗
  3. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    F5 BIG-IP Stack-Based Buffer Overflow Vulnerability
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 2.21% probability · 81.33th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.022130000000; percentile 0.813300000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Mar 27, 2026 · first observed Jul 19, 2026

Exploit likelihood2.21%

FIRST EPSS · score date Aug 27, 2026 · 81.3th percentile · first observed Aug 27, 2026

SeverityCVSS 9.3

f5 · CVSS 4.0 · 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

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 ↗
f5Original assertion
Record text

BigIP APM Vulnerability

Inspect raw assertion
Field
container
Value
BigIP APM Vulnerability
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
F5 BIG-IP Stack-Based Buffer Overflow Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

2.21% probability · 81.33th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.022130000000; percentile 0.813300000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
4Underlying assertions
1Canonical products
4Target 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

2 scope groups

f5 · source assertedF5BIG-IPDirect source scope
Affected: 17.5.0 to before 17.5.1.3 (custom comparison)Affected: 17.1.0 to before 17.1.3 (custom comparison)Affected: 16.1.0 to before 16.1.6.1 (custom comparison)Affected: 15.1.0 to before 15.1.10.8 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "17.5.0", "lessThan": "17.5.1.3", "versionType": "custom"}, {"status": "affected", "version": "17.1.0", "lessThan": "17.1.3", "versionType": "custom"}, {"status": "affected", "version": "16.1.0", "lessThan": "16.1.6.1", "versionType": "custom"}, {"status": "affected", "version": "15.1.0", "lessThan": "15.1.10.8", "versionType": "custom"}]
NVD CPE · APPLICATIONf5big-ip_access_policy_managerVulnerable target · 4 assertions
Any version (unconstrained) (>= 15.1.0, < 15.1.10.8); Any version (unconstrained) (>= 16.1.0, < 16.1.6.1); Any version (unconstrained) (>= 17.1.0, < 17.1.3); Any version (unconstrained) (>= 17.5.0, < 17.5.1.3)Canonical identity product-fe8f45eed4bb3ac6e69f6f6fbf87e9e25862951e870386e176dca756ebfdb2cbLinked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 3
    Logic
    OR
    Version bounds
    from including 17.5.0; through excluding 17.5.1.3
    Match ID
    252ed1a4-5f29-4440-b1ba-9621e6791812
  2. cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    from including 15.1.0; through excluding 15.1.10.8
    Match ID
    a7a0c1ca-edef-463f-b7c8-8b9e67239fc1
  3. cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    from including 17.1.0; through excluding 17.1.3
    Match ID
    96d35435-27a7-4a88-9432-1f5ab0112b8c
  4. cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    from including 16.1.0; through excluding 16.1.6.1
    Match ID
    6494e2a7-1473-46c0-97f8-90827d9466aa

Affected-product evidence

Accepted scope and product mapping

1 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-9aa6446e33f571cc7bda8ab13a2370bdcc16dba7a4e698b5ebc0a2b8d98b481c · product-fe8f45eed4bb3ac6e69f6f6fbf87e9e25862951e870386e176dca756ebfdb2cb

Source class
Nvd cpe vulnerable target
Assertions
4
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
1d49b522-259c-4f19-b906-0f018025fdda6d849de5-5aca-4710-a934-4554ff29459ad61b5514-281b-42c3-b6f7-b533965b33d7f8611ac6-5981-441e-8c5f-57aa300060c2
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
a35de5e2-fb5c-45d8-a389-5b541603b5db

Assessments

CVSS by origin

9.3
f5sirt@f5.comCVSS 4.0 · role Secondary · priority eligiblevalid_matchCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
9.8
f5sirt@f5.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
9.3
f5CVSS 4.0 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8
f5CVSS 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

9.3Priority eligible

f5

CVSS 4.0 · Primary · Original assertion · rank 1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Validation
Valid match
Recomputed
9.3
Decision reason
Evidence supported
Policy
casca-direct-cvss-eligibility-v1
9.8Priority eligible

f5

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
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.