CASCACascade Atlas

Evidence dossier

CVE-2026-28318

SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability

Exploited in the wild (CISA KEV since Jun 5, 2026). SolarWinds reports CVSS 3.1 7.5. EPSS estimates 43.7% exploit likelihood as of Oct 22, 2026.

72.0–77.2Priority evidence range
Evidence through Oct 22, 2026, 6:07 PM UTC

As of Oct 22, 2026

Normalized restatement

SolarWinds Serv-U is susceptible to specially crafted POST requests that crash the Serv-U service without authentication using Content-Encoding: deflate. Mitigation steps are provided to secure customer environments in the SolarWinds Trust Center if you are unable to deploy the update

State
PUBLISHED
Published
Jun 4, 2026
Updated
Oct 21, 2026
Evidence coverage
85%

Evidence chronology

What was known when

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  1. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: SolarWinds Serv-U Uncontrolled Resource Consumption Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    SolarWinds Serv-U Uncontrolled Resource Consumption Vulnerability
    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
    SolarWinds

    Record text: SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability

    Inspect raw assertion
    Field
    container
    Value
    SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 43.65% probability · 98.74th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.436510000000; percentile 0.987400000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Jun 5, 2026 · first observed Sep 1, 2026

Exploit likelihood43.65%

FIRST EPSS · score date Oct 22, 2026 · 98.7th percentile · first observed Oct 22, 2026

SeverityCVSS 7.5

SolarWinds · CVSS 3.1 · first observed Oct 21, 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 statusLast verified source snapshot retained

The last verified source boundary remains in force for this claim.

Revision
evidence-policy-v1.1.0
Cutoff
Oct 22, 2026
Resolution
Review source contract
Exploit likelihoodEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Oct 22, 2026
Resolution
None
Severity assessmentEvidence supported

Eligible evidence is present for this bounded claim.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Oct 22, 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
Oct 22, 2026
Resolution
Resolve identity

Source comparison

Who said what

CISA KEVOriginal assertion
Exploitation cataloged

SolarWinds Serv-U Uncontrolled Resource Consumption Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
SolarWinds Serv-U Uncontrolled Resource Consumption Vulnerability
Source dateFirst 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 ↗
SolarWindsOriginal assertion
Record text

SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability

Inspect raw assertion
Field
container
Value
SolarWinds Serv-U Unauthenticated Denial of Service Vulnerability
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

43.65% probability · 98.74th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.436510000000; percentile 0.987400000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
2Underlying assertions
1Canonical products
2Target 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

SolarWinds · source assertedSolarWindsServ-UDirect source scope
Affected: 0 through 15.5.4 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "0", "versionType": "custom", "lessThanOrEqual": "15.5.4"}]
NVD CPE · APPLICATIONsolarwindsserv-uVulnerable target · 2 assertions
Any version (unconstrained) (< 15.5.4); Version 15.5.4Canonical identity product-5a6bda9ced25850f131d1035dfd39cdbf63cac89e511540f36985b193233345cLinked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:a:solarwinds:serv-u:*:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    through excluding 15.5.4
    Match ID
    0879dda2-3f57-41c7-a689-4b904310687e
  2. cpe:2.3:a:solarwinds:serv-u:15.5.4:-:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    04bc76fb-a18f-4d63-bf35-71e95e1447c0

Affected-product evidence

Accepted scope and product mapping

0 canonical links · 2 source-reported links

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
Oct 22, 2026
Retained assertion IDs
e5383694-e095-4f42-8a98-a87f3c268238
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
Nvd cpe vulnerable target
Assertions
2
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Oct 22, 2026
Retained assertion IDs
e1b3fef5-eb9d-4d56-9a0e-1f5ee3e52579f1e57246-906c-41f2-962c-e2ede44a38f8

Assessments

CVSS by origin

7.5
psirt@solarwinds.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5
SolarWindsCVSS 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:N/I:N/A:H

Direct CVE/CNA normalized decisions

7.5Priority eligible

SolarWinds

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Validation
Valid match
Recomputed
7.5
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.