CVE intelligence and bounded remediation

CVE-2021-37186 — A vulnerability has been identified in LOGO!

Medium CVSS 5.4

A vulnerability has been identified in LOGO! CMR2020 (All versions < V2.2), LOGO! CMR2040 (All versions < V2.2), SIMATIC RTU3010C (All versions < V4.0.9), SIMATIC RTU3030C (All versions < V4.0.9), SIMATIC RTU3031C (All versions < V4.0.9), SIMATIC RTU3041C (All versions < V4.0.9). The underlying TCP/IP stack does not properly calculate the random numbers used as ISN (Initial Sequence Numbers). An adjacent attacker with network access to the LAN interface could interfere with traffic, spoof the connection and gain access to sensitive information.

Severity
Medium
CVSS
5.4 (3.1)
Published
2021-09-14
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-330

Affected products

  • siemens / logo!_cmr2020_firmware
  • siemens / logo!_cmr2040_firmware
  • siemens / simatic_rtu3010c_firmware
  • siemens / simatic_rtu3030c_firmware
  • siemens / simatic_rtu3031c_firmware
  • siemens / simatic_rtu3041c_firmware

Matched remediation archetype

Cryptography, certificate, signature, and channel validation

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Inventory affected algorithms, key uses, trust stores, certificate validation settings, random sources, and plaintext channels across clients and services.
  • Determine which secrets, identities, signatures, or data protections depend on the affected primitive or validation path.
  • Check debug, compatibility, fallback, and hostname or audience override settings in build and runtime configuration.

Remediate safely

  • Use a maintained platform cryptographic API with approved algorithms, modes, parameters, randomness, and full peer identity validation.
  • Remove insecure fallback and validation bypasses; separate keys by purpose and load them from managed secret storage.
  • Plan rotation or reissuance for affected keys, certificates, tokens, hashes, or ciphertext and document compatibility sequencing.

Authoritative sources

Complete CVE record and remediation plan

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