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CVE Record

CVE-2021-1367: Cisco NX-OS Software Protocol Independent Multicast Denial of Service Vulnerability

A vulnerability in the Protocol Independent Multicast (PIM) feature of Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by sending a crafted PIM packet to an affected device. A successful exploit could allow the attacker to cause a traffic loop, resulting in a DoS condition.

MediumCVSS 4.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-1367 is a Cisco NX-OS PIM flaw that can let an unauthenticated attacker on an adjacent network segment disrupt affected devices. The reported impact is availability only: a crafted PIM packet can create a traffic loop and cause a denial of service.

Executive priority

Treat this as a targeted network availability risk, not a broad internet-exposed compromise. Prioritize validation on core or distribution NX-OS devices carrying multicast traffic, because disruption there can affect dependent business services.

Technical view

The vulnerability affects the Protocol Independent Multicast feature in Cisco NX-OS Software and is attributed to insufficient input validation. CVSS 3.1 is 4.3 with adjacent attack vector, low complexity, no privileges, no user interaction, and low availability impact.

Likely exposure

Exposure is likely limited to Cisco NX-OS environments using PIM where an attacker can reach the affected device as an adjacent network peer. The source bundle does not identify affected versions or platforms beyond Cisco NX-OS Software.

Exploitation context

The bundle states exploitation requires sending a crafted PIM packet from an adjacent position. CISA KEV status is false in the provided data, and no cited source here supports active exploitation in the wild.

Researcher notes

Evidence is limited to the CVE record and Cisco advisory reference. The available bundle does not provide affected version ranges, exploit prevalence, or detailed remediation text, so validation should be tied directly to Cisco’s platform-specific advisory data.

Mitigation direction

  • Review Cisco advisory for affected NX-OS platforms and fixed-release guidance.
  • Apply Cisco-recommended fixed software or mitigation for confirmed affected devices.
  • Disable PIM where multicast routing is not operationally required.
  • Restrict adjacency and control-plane access to trusted network segments.
  • Monitor for traffic-loop symptoms and unexpected multicast instability.

Validation and detection

  • Inventory Cisco NX-OS devices and identify where PIM is enabled.
  • Compare device platform and version against Cisco advisory guidance.
  • Confirm only trusted adjacent peers can reach PIM-enabled interfaces.
  • Review network telemetry for traffic loops or multicast-related DoS symptoms.
  • Document any accepted risk where upgrades or mitigations are deferred.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-1367 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.3 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
4.3CVSS 3.1MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L2.81.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4.3Medium
CVSS 3.1 vector shape for CVE-2021-1367Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
CiscoCisco NX-OS Softwaren/aListed
Weakness

CWE details

CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.