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CVE Record

CVE-2021-21777: An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Gr...

An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer 2.3 and development commit 8c73bf3. A specially crafted network request can lead to an out-of-bounds read.

HighCVSS 8.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-21777 affects the OpENer EtherNet/IP stack. A malicious network message to its UDP handler can make vulnerable software read outside expected memory boundaries, with CVSS indicating high availability impact. Organizations using products or firmware that embed this stack should prioritize exposure review.

Executive priority

Treat this as a high-priority exposure-management issue where vulnerable industrial or embedded systems are network reachable. Prioritize inventory and isolation first, then apply vendor-approved updates when identified.

Technical view

The CVE describes an out-of-bounds read in the Ethernet/IP UDP handler of EIP Stack Group OpENer 2.3 and development commit 8c73bf3. The CVSS vector is network-accessible, low complexity, unauthenticated, and no user interaction, with high availability impact.

Likely exposure

Exposure is most likely in industrial, embedded, or control-system products that include OpENer 2.3 or the named development commit and allow network reachability to the affected Ethernet/IP UDP functionality.

Exploitation context

The provided sources do not show known active exploitation, and the CVE is not listed as KEV. The issue is still concerning because the CVSS vector indicates unauthenticated remote reachability with low attack complexity.

Researcher notes

The public bundle identifies the vulnerable component and trigger class but does not provide a confirmed fixed version. CVSS emphasizes availability rather than confidentiality, despite the description calling it information disclosure.

Mitigation direction

  • Inventory firmware, products, or forks using OpENer 2.3 or commit 8c73bf3.
  • Check EIP Stack Group or product-vendor guidance for fixed versions or commits.
  • Restrict access to affected EtherNet/IP UDP services to trusted networks.
  • Remove unnecessary external routing to industrial or embedded device management networks.
  • Monitor affected services for crashes, restarts, or unexplained availability loss.

Validation and detection

  • Confirm whether deployed products embed OpENer 2.3 or the named development commit.
  • Review vendor advisories or SBOMs for OpENer dependency evidence.
  • Map network paths to devices exposing EtherNet/IP UDP functionality.
  • Verify compensating controls limit access to trusted administrative or control networks.
Prepared
Confidence
medium
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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CVE-2021-21777 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.6 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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
8.6CVSS 3.0HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE score

Vulnerability scoring details

Base CVSS 3.0 score

8.6High
CVSS 3.0 vector shape for CVE-2021-21777Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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
n/aEIP Stack GroupEIP Stack Group OpENer 2.3 ,EIP Stack Group OpENer development commit 8c73bf3Listed
Weakness

CWE details

No CWE listed

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