Skip to content
Fencer Vulns
medium 5.4

CVE-2021-37186 json

A vulnerability has been identified in LOGO!

published 2021-09-14 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-23760

cvss
5.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits
0
none known

Summary

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.

Patch / fix

  • 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

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-21-257-13 updated cvss 5.4

Siemens LOGO! CMR and SIMATIC RTU 3000 (Update A)

  • Siemens LOGO! CMR2020 <V2.2 Siemens LOGO! CMR2040 <V2.2
    affected: fixed in V2.2 support.industry.siemens.com
  • Siemens SIMATIC RTU3010C <V4.0.9 Siemens SIMATIC RTU3030C <V4.0.9 Siemens SIMATIC RTU3031C <V4.0.9 Siemens SIMATIC RTU3041C <V4.0.9
    affected: fixed in V4.0.9 support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.4 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD 2.0 4.8 AV:A/AC:L/Au:N/C:P/I:P/A:N

Affected products

  • Siemens LOGO! CMR2020
  • Siemens LOGO! CMR2040
  • Siemens SIMATIC RTU3010C
  • Siemens SIMATIC RTU3030C
  • Siemens SIMATIC RTU3031C
  • Siemens SIMATIC RTU3041C

Classification

Weakness
  • CWE-330 Use of Insufficiently Random Values

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.