CVE-2021-37186

Name: CVE-2021-37186
Creator: NVD / NIST
Published: 2021-09-14T11:15:25.85+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 0.34%

Last modified Jun 17, 2026

CVE-2021-37186 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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). EPSS estimates a 0.34% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS Probability

0.34%

26.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Siemens	Logo\! Cmr2020 Firmware	< 2.2
Siemens	Logo\! Cmr2040 Firmware	< 2.2
Siemens	Simatic Rtu3010c Firmware	< 4.0.9
Siemens	Simatic Rtu3030c Firmware	< 4.0.9
Siemens	Simatic Rtu3031c Firmware	< 4.0.9
Siemens	Simatic Rtu3041c Firmware	< 4.0.9

References

https://cert-portal.siemens.com/productcert/pdf/ssa-316383.pdfPatch, Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-316383.pdfPatch, Vendor Advisory

Timeline

Published: Sep 14, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-37186?

How severe is CVE-2021-37186?

CVE-2021-37186 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.

How do I fix CVE-2021-37186?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-37186?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST