CASCACascade Atlas

Evidence dossier

CVE-2020-3566

Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Exploited in the wild (CISA KEV since Nov 3, 2021). NVD reports CVSS 3.1 8.6. EPSS estimates 3.7% exploit likelihood as of Aug 27, 2026.

68.0–69.5Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

A vulnerability in the Distance Vector Multicast Routing Protocol (DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to exhaust process memory of an affected device. The vulnerability is due to insufficient queue management for Internet Group Management Protocol (IGMP) packets. An attacker could exploit this vulnerability by sending crafted IGMP traffic to an affected device. A successful exploit could allow the attacker to cause memory exhaustion, resulting in instability of other processes. These processes may include, but are not limited to, interior and exterior routing protocols. Cisco will release software updates that address this vulnerability.

State
PUBLISHED
Published
Aug 29, 2020
Updated
Oct 21, 2025
Evidence coverage
92%

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
    cisco

    Record text: Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

    Inspect raw assertion
    Field
    container
    Value
    Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability
    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: Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 3.7% probability · 88.92th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.037020000000; percentile 0.889200000000
    Original evidence ↗
ExploitationCatalog member

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

Exploit likelihood3.70%

FIRST EPSS · score date Aug 27, 2026 · 88.9th percentile · first observed Aug 27, 2026

SeverityCVSS 8.6

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

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 ↗
ciscoOriginal assertion
Record text

Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Inspect raw assertion
Field
container
Value
Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability
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

Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

3.7% probability · 88.92th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.037020000000; percentile 0.889200000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
10Underlying assertions
10Canonical products
1Target assertions
9Constraint assertions

Grouped from 2 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

11 scope groups

cisco · source assertedCiscoCisco IOS XR SoftwareDirect source scope
Affected: n/a
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "n/a"}]
NVD CPE · HARDWAREciscoasr_9001Environmental constraint · 1 assertions
Version not applicableCanonical identity product-cbb6a64cd76f93814f9ffbd38fad8ca11ba8e81e213e4e169a5ce30f53509e93Linked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9001:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    324c97e6-1810-404f-9f45-6240f99ff039
NVD CPE · HARDWAREciscoasr_9006Environmental constraint · 1 assertions
Version not applicableCanonical identity product-e34ba24d6024231202802383edcf903e9a0f790d71683e4a0b3ce73f75b2d9c0Linked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9006:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    57eb55bb-41b7-40a1-b6f5-142fe8ab4c16
NVD CPE · HARDWAREciscoasr_9010Environmental constraint · 1 assertions
Version not applicableCanonical identity product-cecc7d25e1f52a276317b8d7c1142df49b9856fa88a4e9398bb5bb5a8da98ebdLinked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9010:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 2
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    433f4a82-04a4-4eaa-8c19-f7581dcd8d29
NVD CPE · HARDWAREciscoasr_9901Environmental constraint · 1 assertions
Version not applicableCanonical identity product-500631d9637d1714be4d575b52fe15017bd4ed71ab34207139105753e0023ba5Linked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9901:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 3
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    2d5e60ab-94ff-448a-89d8-5d2197e21c74
NVD CPE · HARDWAREciscoasr_9904Environmental constraint · 1 assertions
Version not applicableCanonical identity product-a422f65dc74a0df045ed5464b21e82dae402fb78a25630e694496c8a03b80500Linked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9904:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 4
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    a93212a4-50ab-42e7-89a4-5fbbaea050c3
NVD CPE · HARDWAREciscoasr_9906Environmental constraint · 1 assertions
Version not applicableCanonical identity product-209e640d48c2b954968672513e1b3f876e7b6e5568b38e5725d5c68bbb74bf4fLinked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9906:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 5
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    eda53a61-98b3-458c-8893-61cd7d6b1e48
NVD CPE · HARDWAREciscoasr_9910Environmental constraint · 1 assertions
Version not applicableCanonical identity product-28be360820ad2d572519a9fb1645fb8e0187dba6d2dd0b67846515e298438ebfLinked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9910:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 6
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    f396564e-b477-4a27-a189-ceb737552e25
NVD CPE · HARDWAREciscoasr_9912Environmental constraint · 1 assertions
Version not applicableCanonical identity product-f8227c000eef76f989db048ff31d4107f58c3d82389c725c8c58e4a8bb2dde45Linked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9912:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 7
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    5445cc54-acfb-4070-af26-f91feaa85181
NVD CPE · HARDWAREciscoasr_9922Environmental constraint · 1 assertions
Version not applicableCanonical identity product-13a448fd7161a05877ce8fbef8006e9e7d23a9f8a0f8f09c1b473c0db973d8e7Linked exact
Scope constrained
Inspect raw assertion
  1. cpe:2.3:h:cisco:asr_9922:-:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Environmental constraint
    Configuration
    0 · node/1 · match 8
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    d7aa58e5-d7e1-48cf-93ff-c60eb85b2bc7
NVD CPE · OPERATING SYSTEMciscoios_xrVulnerable target · 1 assertions
Version 6.4.2Canonical identity product-a70ec7fc7d464008f2ddd19bcef52a09c444f9b0cbe4a0ab86461995673f4a82Linked exact
Scope supported
Inspect raw assertion
  1. cpe:2.3:o:cisco:ios_xr:6.4.2:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    e67f538a-3e1a-4749-bb8d-4f8043653b6e

Affected-product evidence

Accepted scope and product mapping

1 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-0774b265c0e837e737aaf99ed0f2450c048e61f34267ca59d8623878b839334e · product-a70ec7fc7d464008f2ddd19bcef52a09c444f9b0cbe4a0ab86461995673f4a82

Source class
Nvd cpe vulnerable target
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
d078b86c-ea6c-4dbb-9cb1-6908049fd1b6
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
493b20d6-39e9-42f3-a402-a9eb2503ca3d

Assessments

CVSS by origin

8.6
NVDCVSS 3.1 · role Primary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
7.8
NVDCVSS 2.0 · role Primary · priority eligiblevalid_matchAV:N/AC:L/Au:N/C:N/I:N/A:C
8.6
psirt@cisco.comCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
8.6
ciscoCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Direct CVE/CNA normalized decisions

8.6Priority eligible

cisco

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Validation
Valid match
Recomputed
8.6
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.