CVE-2021-37186

mediumpriority · track · 22OT risk · elevatedEPSS 0.004 · 29 %ileDEEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.36% (29th) EPSS

CVSS 4.8 · medium

Is it mine?

36 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · cisa_csaf_ot · nvd

EPSS · scored 2026-10-27

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.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedLOGO! CMR2020siemens_psirt
Update to V2.2 or later version
https://support.industry.siemens.com/cs/ww/en/view/109800267/
FixedLOGO! CMR2040siemens_psirt
Update to V2.2 or later version
https://support.industry.siemens.com/cs/ww/en/view/109800267/
FixedSIMATIC RTU3010Csiemens_psirt
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedSIMATIC RTU3030Csiemens_psirt
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedSIMATIC RTU3031Csiemens_psirt
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedSIMATIC RTU3041Csiemens_psirt
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedLOGO! CMR2020cisa_csaf_ot
Update to V2.2 or later version
https://support.industry.siemens.com/cs/ww/en/view/109800267/
FixedLOGO! CMR2040cisa_csaf_ot
Update to V2.2 or later version
https://support.industry.siemens.com/cs/ww/en/view/109800267/
FixedSIMATIC RTU3010Ccisa_csaf_ot
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedSIMATIC RTU3030Ccisa_csaf_ot
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedSIMATIC RTU3031Ccisa_csaf_ot
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/
FixedSIMATIC RTU3041Ccisa_csaf_ot
Update to V4.0.9 or later version
https://support.industry.siemens.com/cs/ww/en/view/109802779/

cvss

Technical severity, 0–10. One row per scoring source.

5.4

010

base score 0–10 · higher = more severe · hover a vector to decode

v2.04.8mediumAV:A/AC:L/Au:N/C:P/I:P/A:Nprimary · NVD / NIST USexploitability 6.5 · impact 4.9

v3.15.4mediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 2.5

v3.15.4mediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:Csecondary · CISA US

v3.15.4mediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:Csecondary · Siemens ProductCERT DE

v3.15mediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-330USprimaryCWE-330USCWE-330US

affected products (36)

Products and version ranges known to be affected.

LOGO! CMR2020 (6GK7142-7BX00-0AX0)all versionscisa_csaf_otUS
LOGO! CMR2040 (6GK7142-7EX00-0AX0)all versionscisa_csaf_otUS
SIMATIC RTU3010C (6NH3112-0BA00-0XX0)all versionscisa_csaf_otUS
SIMATIC RTU3030C (6NH3112-3BA00-0XX0)all versionscisa_csaf_otUS
SIMATIC RTU3031C (6NH3112-3BB00-0XX0)all versionscisa_csaf_otUS
SIMATIC RTU3041C (6NH3112-4BB00-0XX0)all versionscisa_csaf_otUS
Siemens LOGO! CMR2020< V2.2cisa_csaf_otUS
Siemens LOGO! CMR2040< V2.2cisa_csaf_otUS
Siemens SIMATIC RTU3010C< V4.0.9cisa_csaf_otUS
Siemens SIMATIC RTU3030C< V4.0.9cisa_csaf_otUS
Siemens SIMATIC RTU3031C< V4.0.9cisa_csaf_otUS
Siemens SIMATIC RTU3041C< V4.0.9cisa_csaf_otUS
Siemens LOGO! CMR2020All versions → V2.2enisa_euvdEU
Siemens LOGO! CMR2040All versions → V2.2enisa_euvdEU
Siemens SIMATIC RTU3010CAll versions → V4.0.9enisa_euvdEU
Siemens SIMATIC RTU3030CAll versions → V4.0.9enisa_euvdEU
Siemens SIMATIC RTU3031CAll versions → V4.0.9enisa_euvdEU
Siemens SIMATIC RTU3041CAll versions → V4.0.9enisa_euvdEU
siemens logo! cmr2020 firmware< 2.2nvdUScpe:2.3:o:siemens:logo\!_cmr2020_firmware:*:*:*:*:*:*:*:*
siemens logo! cmr2040 firmware< 2.2nvdUScpe:2.3:o:siemens:logo\!_cmr2040_firmware:*:*:*:*:*:*:*:*

showing 20 of 36

advisories (2)

Vendor and ecosystem advisories describing this.

SSA-316383SSA-316383: NumberJack Vulnerability in LOGO! CMR and SIMATIC RTU 3000 devices2021-09-14csaf · siemens_psirtDE
A vulnerability has been identified in the underlying TCP/IP stack of LOGO! CMR and SIMATIC RTU 3000 devices. It could allow an attacker with network access to the LAN interface of an affected device to hijack an ongoing connection or spoof a new one. The WAN interface, however, is not affected. Siemens has released updates for the affected products and recommends to update to the latest versions.
ICSA-21-257-13Siemens LOGO! CMR and SIMATIC RTU 3000 (Update A)2021-09-14icsa · cisa_csaf_otUS
A vulnerability has been identified in the underlying TCP/IP stack of LOGO! CMR and SIMATIC RTU 3000 devices. It could allow an attacker with network access to the LAN interface of an affected device to hijack an ongoing connection or spoof a new one. The WAN interface, however, is not affected. Siemens has released updates for the affected products and recommends to update to the latest versions.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd cisa_csaf_ot nvd siemens_psirt NVD CVE.org MITRE

published 2021-09-14modified 2026-06-17

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references (8)

External citations — patches, advisories, analysis.

scry

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