Security readout for executives and security teams
Plain-English summary
This vulnerability can let an unauthenticated network attacker crash affected OpENer EtherNet/IP implementations with a crafted packet. The business risk is service disruption in systems that use this open-source EtherNet/IP stack, especially where industrial control networks are reachable.
Executive priority
Treat this as a high-priority availability risk for affected operational technology environments. It does not indicate data theft, but disruption to industrial services can still create material business impact.
Technical view
CVE-2021-27500 is a reachable assertion in EIPStackGroup OpENer EtherNet/IP commits and versions before February 10, 2021. The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating unauthenticated network-triggered denial of service with high availability impact.
Likely exposure
Exposure is most likely in industrial or embedded systems that include OpENer EtherNet/IP versions or commits before February 10, 2021 and accept network traffic to the stack.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. They support a network-reachable denial-of-service condition from a crafted packet, but not public weaponization or exploitation in the wild.
Researcher notes
Evidence is limited to the CVE description, CVSS data, affected product naming, CISA ICS advisory reference, and OpENer repository reference. Avoid assuming downstream vendor impact without confirming embedded OpENer usage and version provenance.
Mitigation direction
- Inventory products or builds that include EIPStackGroup OpENer EtherNet/IP.
- Verify whether deployed code predates February 10, 2021.
- Check the CISA advisory and OpENer repository for vendor remediation guidance.
- Update or rebuild from a non-affected OpENer version where supported.
- Restrict network reachability to EtherNet/IP services where operationally feasible.
Validation and detection
- Confirm OpENer dependency versions, commit dates, or bundled source snapshots.
- Review SBOMs and firmware manifests for EIPStackGroup OpENer references.
- Map where EtherNet/IP traffic reaches affected devices or services.
- Validate availability monitoring for systems using the stack.
- Document compensating controls if immediate update is not possible.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-617: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-27500 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.cisa.gov/uscert/ics/advisories/icsa-21-105-02CVE reference · x_refsource_CONFIRM
- https://github.com/EIPStackGroup/OpENerCVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Reachable Assertion
Reachable Assertion represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.