Security readout for executives and security teams
Plain-English summary
Some Siemens LOGO! CMR and SIMATIC RTU devices used in industrial environments generate TCP connection identifiers with insufficient randomness. An attacker already on the same local network could potentially impersonate or interfere with traffic and see sensitive information.
Executive priority
Treat as a targeted OT network risk, not a broad internet emergency based on available evidence. Prioritize sites with flat local networks or third-party LAN access, then schedule firmware updates and segmentation checks through normal industrial change control.
Technical view
CVE-2021-37186 is a CWE-330 weakness in the underlying TCP/IP stack ISN generation for LOGO! CMR2020/2040 before V2.2 and SIMATIC RTU3010C/3030C/3031C/3041C before V4.0.9. The source states an adjacent LAN attacker could interfere with traffic, spoof connections, and gain sensitive information.
Likely exposure
Exposure is mainly OT networks where affected Siemens LOGO! CMR or SIMATIC RTU devices are reachable from other LAN hosts. The source does not state internet exposure. Risk rises if vendor devices share a flat network with contractors, office IT, wireless segments, or compromised endpoints.
Exploitation context
The provided sources do not report active exploitation, and the CVE is not flagged as KEV. The attack requires adjacent network access to the LAN interface, which limits reach but can still matter in poorly segmented industrial networks.
Researcher notes
Evidence is limited to the CVE description and Siemens advisory reference in the supplied bundle. No CVSS vector, exploit maturity, or detailed mitigation text was provided. Avoid assuming broader product impact beyond the six named Siemens models and version ranges.
Mitigation direction
- Upgrade LOGO! CMR2020 and CMR2040 to V2.2 or later.
- Upgrade affected SIMATIC RTU models to V4.0.9 or later.
- Review Siemens SSA-316383 for product-specific update guidance.
- Restrict LAN access to affected devices to trusted OT hosts only.
- Segment OT networks from office, guest, wireless, and contractor networks.
Validation and detection
- Inventory Siemens LOGO! CMR and SIMATIC RTU devices in OT environments.
- Record exact firmware versions for each affected product model.
- Confirm affected devices are not below the fixed version thresholds.
- Map which LAN segments can reach each device interface.
- Review network monitoring for unexpected spoofing or session anomalies.
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-330: 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-2021-37186 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
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://cert-portal.siemens.com/productcert/pdf/ssa-316383.pdfCVE 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.
Use of Insufficiently Random Values
Use of Insufficiently Random Values represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.