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CVE Record

CVE-2021-37206: A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SI...

A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP100 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP300 (All versions < V8.80). Received webpackets are not properly processed. An unauthenticated remote attacker with access to any of the Ethernet interfaces could send specially crafted packets to force a restart of the target device.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This issue can let an unauthenticated attacker who can reach a SIPROTEC 5 relay Ethernet interface force the relay to restart. In power environments, unexpected relay restarts can affect protection availability and operational continuity, even without evidence of data theft or code execution.

Executive priority

Treat this as a high-priority OT availability risk where affected relays support critical protection functions. Prioritize plants or substations with reachable Ethernet interfaces and limited segmentation. There is no sourced evidence of active exploitation in the provided bundle.

Technical view

CVE-2021-37206 affects Siemens SIPROTEC 5 relays with CPU variants CP050, CP100, and CP300 on versions below V8.80. The weakness is improper processing of received packets, mapped to CWE-20, allowing specially crafted network packets to trigger a device restart.

Likely exposure

Exposure is limited to Siemens SIPROTEC 5 relays using CP050, CP100, or CP300 CPU variants below V8.80, especially where Ethernet interfaces are reachable from shared, routable, or insufficiently segmented OT networks.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. The described attack is unauthenticated and remote, but requires network access to one of the relay Ethernet interfaces. No exploit maturity, public exploit, or CVSS score is provided in the bundle.

Researcher notes

Evidence is concise and vendor-centered. The main technical facts are affected CPU variants, versions below V8.80, CWE-20, unauthenticated Ethernet reachability, crafted packet handling, and forced restart outcome. The bundle does not provide CVSS, packet details, exploit status, or complete mitigation text.

Mitigation direction

  • Inventory SIPROTEC 5 relays and identify CP050, CP100, and CP300 CPU variants.
  • Check whether relay firmware is below V8.80.
  • Consult Siemens SSA-500748 for the supported remediation path.
  • Restrict Ethernet interface access to trusted OT management and protection networks.
  • Monitor affected relays for unexpected restart or availability events.

Validation and detection

  • Confirm product model, CPU variant, and firmware version from asset records or device management tools.
  • Map which relay Ethernet interfaces are reachable from each OT network zone.
  • Review logs or operations records for unexplained relay restarts.
  • Verify Siemens advisory applicability before scheduling firmware or operational changes.
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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cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-37206 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
SiemensSIPROTEC 5 relays with CPU variants CP050All versions < V8.80Listed
SiemensSIPROTEC 5 relays with CPU variants CP100All versions < V8.80Listed
SiemensSIPROTEC 5 relays with CPU variants CP300All versions < V8.80Listed
Weakness

CWE details

CWE-20

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