Security readout for executives and security teams
Plain-English summary
CVE-2021-21964 affects Sealevel Systems SeaConnect 370W v1.3.34. A remote, unauthenticated attacker could send crafted network packets to disrupt the device. For organizations using this industrial connectivity equipment, the main business risk is loss of availability for connected operations, with limited confidentiality and integrity impact noted in the CVSS vector.
Executive priority
Prioritize remediation or isolation where affected devices support operational processes or are reachable beyond tightly controlled networks. This is a high availability risk, not currently a confirmed actively exploited issue in the supplied sources.
Technical view
The issue is a denial-of-service vulnerability in the Modbus configuration functionality. The CVSS v3.0 score is 8.6: network reachable, low complexity, no privileges, no user interaction, unchanged scope, low confidentiality and integrity impact, and high availability impact. The source bundle maps it to CWE-284.
Likely exposure
Exposure is likely limited to environments running SeaConnect 370W v1.3.34, especially if the device or its Modbus configuration interface is reachable from untrusted networks. The bundle does not identify other affected versions or products.
Exploitation context
The sources describe exploitation through specially crafted network packets, but do not provide evidence of active exploitation. The CVE is not marked as CISA KEV in the supplied bundle. Treat internet or broadly routed management exposure as higher urgency.
Researcher notes
Evidence is specific to SeaConnect 370W v1.3.34 and Modbus configuration handling. The bundle does not name a patch, fixed version, proof of active exploitation, or broader affected product set. Avoid expanding scope beyond the cited product without vendor confirmation.
Mitigation direction
- Identify any SeaConnect 370W devices and confirm firmware version 1.3.34 exposure.
- Restrict Modbus configuration access to trusted management networks only.
- Block untrusted network access to affected device management services.
- Check Sealevel and Talos guidance for any fixed firmware or vendor mitigation.
- Monitor affected devices for unexpected resets, outages, or configuration service failures.
Validation and detection
- Inventory OT and network segments for SeaConnect 370W deployments.
- Confirm whether version 1.3.34 is present on any device.
- Review firewall rules for external or cross-segment reachability to device configuration services.
- Check logs and monitoring for unexplained availability loss around affected devices.
- Document compensating controls where vendor remediation is unavailable.
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-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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-2021-21964 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 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H3.94.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.6HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1392CVE reference · x_refsource_MISC
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.
Improper Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.