CASCACascade Atlas

Evidence dossier

CVE-2021-35211

Serv-U Remote Memory Escape Vulnerability

Exploited in the wild (CISA KEV since Nov 3, 2021). NVD reports CVSS 3.1 10.0. Severity assessments differ within at least one CVSS version. EPSS estimates 91.2% exploit likelihood as of Aug 27, 2026.

84.2–88.3Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

Microsoft discovered a remote code execution (RCE) vulnerability in the SolarWinds Serv-U product utilizing a Remote Memory Escape Vulnerability. If exploited, a threat actor may be able to gain privileged access to the machine hosting Serv-U Only. SolarWinds Serv-U Managed File Transfer and Serv-U Secure FTP for Windows before 15.2.3 HF2 are affected by this vulnerability.

State
PUBLISHED
Published
Jul 14, 2021
Updated
Oct 21, 2025
Evidence coverage
83%

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
    SolarWinds

    Record text: Serv-U Remote Memory Escape Vulnerability

    Inspect raw assertion
    Field
    container
    Value
    Serv-U Remote Memory Escape Vulnerability
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: SolarWinds Serv-U Remote Code Execution Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    SolarWinds Serv-U Remote Code Execution Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 91.16% probability · 99.8th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.911600000000; percentile 0.998000000000
    Original evidence ↗

Assessments differ

NVD10.0CVSS 3.1 · source date omitted
NVD10.0CVSS 2.0 · source date omitted
psirt@solarwinds.com9.0CVSS 3.1 · source date omitted

Values are shown separately by source and CVSS version.

ExploitationCatalog member

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

Exploit likelihood91.16%

FIRST EPSS · score date Aug 27, 2026 · 99.8th 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 ↗
SolarWindsOriginal assertion
Record text

Serv-U Remote Memory Escape Vulnerability

Inspect raw assertion
Field
container
Value
Serv-U Remote Memory Escape Vulnerability
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

SolarWinds Serv-U Remote Code Execution Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
SolarWinds Serv-U Remote Code Execution Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

91.16% probability · 99.8th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.911600000000; percentile 0.998000000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
3Underlying assertions
1Canonical products
3Target 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-U Managed File Transfer Server and Serv-U Secured FTPDirect source scope
Affected: SolarWinds Serv-U to before 15.2.3 HF1 (custom comparison)
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "SolarWinds Serv-U", "lessThan": "15.2.3 HF1", "versionType": "custom"}]
NVD CPE · APPLICATIONsolarwindsserv-uVulnerable target · 3 assertions
Any version (unconstrained) (< 15.2.3); Version 15.2.3Canonical 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 15.2.3
    Match ID
    66a68531-7831-4875-b0ab-215c3e5a62b6
  2. cpe:2.3:a:solarwinds:serv-u:15.2.3:-:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    9e8b32a1-90c1-4901-9b66-fa72e5787450
  3. cpe:2.3:a:solarwinds:serv-u:15.2.3:hotfix1:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    92569e9a-911c-4704-a962-047ff5e0e2cf

Affected-product evidence

Accepted scope and product mapping

1 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-391e7faeab524390123e1ed5f782756e82c750d283ae0f54737c4a4dc9612f6d · product-5a6bda9ced25850f131d1035dfd39cdbf63cac89e511540f36985b193233345c

Source class
Nvd cpe vulnerable target
Assertions
3
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
74de6172-30ad-48df-a5aa-3c1beecc7a3f829ee084-f714-4e3a-820d-a3d308868ab9b9ec68c1-81ea-4ce8-b69d-312d4079cc85
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
5c2f7765-0884-423b-b574-a4a6f48adc39

Assessments

CVSS by origin

10.0
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
10.0
NVDCVSS 2.0 · role Primary · priority eligiblevalid_matchAV:N/AC:L/Au:N/C:C/I:C/A:C
9.0
psirt@solarwinds.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
9.0
SolarWindsCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Direct CVE/CNA normalized decisions

9.0Priority eligible

SolarWinds

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Validation
Valid match
Recomputed
9.0
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.