Security readout for executives and security teams
Plain-English summary
This CVE can let an unauthenticated network user crash affected industrial devices using Hilscher EtherNet/IP Core V2. Sources also mention memory corruption and possible code injection, but provide limited operational detail. The main business concern is loss of availability in OT environments that rely on affected Hilscher-based or Pepperl+Fuchs devices.
Executive priority
Prioritize this for OT environments where affected devices support production, safety-adjacent workflows, or automated material handling. The issue is high severity because a remote unauthenticated condition can cause unrecoverable crashes, creating downtime risk even when confidentiality and data integrity impacts are not shown.
Technical view
CVE-2021-20987 affects Hilscher EtherNet/IP Core V2 before V2.13.0.21 and listed Pepperl+Fuchs PCV/PXV/PGV and WCS products. It is a CWE-787 out-of-bounds write issue tied to a specific CIP service, with CVSS 8.6, network attack vector, no privileges, no user interaction, and high availability impact.
Likely exposure
Exposure is most likely in industrial networks running affected EtherNet/IP devices, especially Hilscher Core V2 integrations before V2.13.0.21 or the listed Pepperl+Fuchs identification and positioning products. Internet exposure is not stated in the sources; assess reachability from engineering workstations, vendor remote access paths, and less-trusted plant network segments.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The CVSS vector indicates network-reachable, low-complexity exploitation without authentication or user interaction. Public details are limited, so treat this as a serious availability risk without assuming confirmed in-the-wild exploitation.
Researcher notes
Evidence supports denial of service, memory corruption, and possible code injection, but the bundle does not include exploit details, PoC status, or confirmed active exploitation. Validation should focus on version identification, affected product mapping, and network reachability rather than attempting unsafe protocol testing against production equipment.
Mitigation direction
- Upgrade Hilscher EtherNet/IP Core V2 to V2.13.0.21 or later where applicable.
- Check Hilscher, VDE, and Pepperl+Fuchs guidance for device-specific firmware updates.
- Restrict EtherNet/IP and CIP access to trusted OT hosts only.
- Segment affected devices from enterprise, guest, and internet-reachable networks.
- Increase monitoring for unexpected device crashes, hangs, or unrecoverable faults.
Validation and detection
- Inventory Hilscher EtherNet/IP Core V2 usage and affected Pepperl+Fuchs models.
- Compare installed firmware or stack versions against V2.13.0.21 and vendor advisories.
- Map which hosts can reach affected devices over industrial network paths.
- Review device logs and maintenance records for unexplained crashes or reboots.
- Confirm compensating controls block untrusted network access to EtherNet/IP services.
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-787: 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-2021-20987 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
- 8.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.6HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.hilscher.com/pages/viewpage.action?pageId=108969480CVE reference · x_refsource_CONFIRM
- https://cert.vde.com/en-us/advisories/vde-2021-007CVE 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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.