CASCACascade Atlas

Evidence dossier

CVE-2018-13383

A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the…

Exploited in the wild (CISA KEV since Jan 10, 2022). NVD reports CVSS 3.1 6.5. Severity assessments differ within at least one CVSS version. EPSS estimates 33.6% exploit likelihood as of Aug 27, 2026.

65.9–72.7Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.

State
PUBLISHED
Published
May 29, 2019
Updated
Oct 21, 2025
Evidence coverage
85%

Evidence chronology

What was known when

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  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
    CVE Program

    Record text: CVE Program Container

    Inspect raw assertion
    Field
    container
    Value
    CVE Program Container
    Original evidence ↗
  3. Source dateSource date omittedFirst observed by CASCA
    fortinet

    Record text: A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.

    Inspect raw assertion
    Field
    container
    Value
    A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: Fortinet FortiOS and FortiProxy Out-of-bounds Write

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Fortinet FortiOS and FortiProxy Out-of-bounds Write
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 33.65% probability · 98.26th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.336470000000; percentile 0.982600000000
    Original evidence ↗

Assessments differ

NVD6.5CVSS 3.1 · source date omitted
NVD4.3CVSS 2.0 · source date omitted
psirt@fortinet.com4.3CVSS 3.1 · source date omitted

Values are shown separately by source and CVSS version.

ExploitationCatalog member

CISA KEV · catalog date Jan 10, 2022 · first observed Jul 19, 2026

Exploit likelihood33.65%

FIRST EPSS · score date Aug 27, 2026 · 98.3th percentile · first observed Aug 27, 2026

SeverityAssessments differ

NVD · CVSS 3.1 · first observed Jul 19, 2026 · values shown separately below

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 assessmentAssessments differ

Eligible assertions materially conflict and remain visible side by side.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Aug 27, 2026
Resolution
Resolve conflict
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 ↗
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 ↗
fortinetOriginal assertion
Record text

A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.

Inspect raw assertion
Field
container
Value
A heap buffer overflow in Fortinet FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier and FortiProxy 2.0.0, 1.2.8 and earlier in the SSL VPN web portal may cause the SSL VPN web service termination for logged in users due to a failure to properly handle javascript href data when proxying webpages.
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

Fortinet FortiOS and FortiProxy Out-of-bounds Write

Inspect raw assertion
Field
observed_exploitation
Value
Fortinet FortiOS and FortiProxy Out-of-bounds Write
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

33.65% probability · 98.26th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.336470000000; percentile 0.982600000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
6Underlying assertions
2Canonical products
6Target 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

3 scope groups

fortinet · source assertedFortinetFortinet FortiOS and FortiProxyDirect source scope
Affected: FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier, FortiProxy 2.0.0, 1.2.8 and earlier
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "FortiOS 6.0.0 through 6.0.4, 5.6.0 through 5.6.10, 5.4.0 through 5.4.12, 5.2.14 and earlier, FortiProxy 2.0.0, 1.2.8 and earlier"}]
NVD CPE · OPERATING SYSTEMfortinetfortiosVulnerable target · 4 assertions
Any version (unconstrained) (>= 5.2.0, < 5.2.15); Any version (unconstrained) (>= 5.4.0, < 5.4.13); Any version (unconstrained) (>= 5.6.0, < 5.6.11); Any version (unconstrained) (>= 6.0.0, < 6.0.5)Canonical identity product-d06140244cc5e972beb67f7de823109a7332f0ff670c2c5c21938de936e3f496Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 3
    Logic
    OR
    Version bounds
    from including 5.4.0; through excluding 5.4.13
    Match ID
    b07b6e15-30ae-44e6-8009-a30fd3e5ccd3
  2. cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 5
    Logic
    OR
    Version bounds
    from including 6.0.0; through excluding 6.0.5
    Match ID
    d37f1481-e7a7-4428-89c9-5df9d206d056
  3. cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 4
    Logic
    OR
    Version bounds
    from including 5.6.0; through excluding 5.6.11
    Match ID
    9093be81-687c-4ccb-834a-be49cee367c5
  4. cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    from including 5.2.0; through excluding 5.2.15
    Match ID
    5cc2097e-ba3d-4596-b4e4-5fb0ddcae2fe
NVD CPE · APPLICATIONfortinetfortiproxyVulnerable target · 2 assertions
Any version (unconstrained) (< 1.2.9); Version 2.0.0Canonical identity product-53e2c632c140b04469e646fdc096d80536975303740dc515e32352dc87ed2607Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:fortinet:fortiproxy:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    through excluding 1.2.9
    Match ID
    4b47708e-8a92-4767-8685-49c3143d0920
  2. cpe:2.3:a:fortinet:fortiproxy:2.0.0:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    f3dd97ea-92ad-4eb1-b731-261f40bfc4bb

Affected-product evidence

Accepted scope and product mapping

2 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-a82aadab6a309189375ddbea412e10a6aef0b5411f0ae9526eeafad0e62c10e6 · product-53e2c632c140b04469e646fdc096d80536975303740dc515e32352dc87ed2607

Source class
Nvd cpe vulnerable target
Assertions
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
4a286ff7-ac05-42e5-bbe8-bdbacfec47b49542a583-c7b1-43e7-a068-2e1ac977642c
Mapping establishedEvidence supported

vendor-a82aadab6a309189375ddbea412e10a6aef0b5411f0ae9526eeafad0e62c10e6 · product-d06140244cc5e972beb67f7de823109a7332f0ff670c2c5c21938de936e3f496

Source class
Nvd cpe vulnerable target
Assertions
4
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
1059df37-3b35-4a1c-93f7-4d89a2965bc27a26b9cc-87bd-4ddd-81c4-3b002e9ea307aac41917-ed84-45c5-986b-2108480ca30ce63ce79f-3c3b-4a1c-a23e-70fe5131c2c3
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
c179d502-b3b3-486d-8b09-e5191b202b96

Assessments

CVSS by origin

6.5
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3
NVDCVSS 2.0 · role Primary · priority eligiblevalid_matchAV:N/AC:M/Au:N/C:N/I:N/A:P
4.3
psirt@fortinet.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
4.3
fortinetCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Direct CVE/CNA normalized decisions

4.3Priority eligible

fortinet

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Validation
Valid match
Recomputed
4.3
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.