Home/CVE/A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R
CVE
CVE-2021-31890
A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R
A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303), PLUSCONTROL 1st Gen (All versions), SIMOTICS CONNECT 400 (All versions < V0.5.0.0), SIMOTICS CONNECT 400 (All versions < V1.0.0.0). The total length of an TCP payload (set in the IP header) is unchecked. This may lead to various side effects, including Information Leak and Denial-of-Service conditions, depending on the network buffer organization in memory.
(FSMD-2021-0017)
HIGH · CVSS 7.5
EPSS 0.0215
EPSS exploitation odds2.15% · top 19%
Schedule remediation
- CVSS base score ≥ 7.0
No Sigma yet — build one →
YARA rules0
Look this up elsewhere - one-click external pivots
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How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2021-31890, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked.
EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal.
CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score.
Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits.
PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
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Exploitation momentum
655 days of EPSSdormant
Flat and low - no real exploitation pressure. This reads the direction and speed of EPSS over time, which can move before EPSS itself peaks or before CISA lists it.
EPSS exploitation probability
2.15%
Top 19%odds of exploitation in the next 30 days
CVSS metric silhouette
shape grows toward worst-case
SSVC triage
No SSVC vulnrichment for this CVE. CISA's Vulnrichment program scores newer CVEs (~2024 onwards) plus selected older critical ones. Use the EPSS probability + KEV status to triage instead.
CVSS vector breakdown
Exploitability - how they get in
Attack Vector
Network
Adjacent
Local
Physical
Attack Complexity
Low
High
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Impact - what breaks
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
VECTOR
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HLifecycle
- 09 Nov 2021Published to NVD
- 17 Jun 2026Last modified
Every entry is a recorded date - NVD publish/modify, CISA KEV add, public exploit disclosure. No inferred events.
Attack path
Full kill chain
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ATT&CK techniques
1Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.
▤ Build a SIEM detection for these techniques⬡
Weakness Classification
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Affected Products & Versions
11siemens capital vstarall versions
siemens nucleus netall versions
siemens nucleus readystart v3< 2017.02.4
siemens nucleus source codeall versions
siemens apogee pxc compact firmwareall versions
siemens apogee pxc modular firmwareall versions
siemens talon tc compact firmwareall versions
siemens talon tc modular firmwareall versions
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Related CVEs
8CVEs linked to this one by a shared weakness (CWE) or affected product - joins on data already in the engine, with the reason shown per row.
CVE-2022-40957
Inconsistent data in instruction and data cache when creating wasm code could le...
same CWE-240
MEDIUM
CVE-2023-39914
NLnet Labs' bcder library up to and including version 0.7.2 panics while decodin...
same CWE-240
HIGH
CVE-2023-39915
NLnet Labs' Routinator up to and including version 0.12.1 may crash when trying ...
same CWE-240
HIGH
CVE-2025-4321
In a Bluetooth device, using RS9116-WiseConnect SDK experiences a Denial of Serv...
same CWE-240
CVE-2019-13939
A vulnerability has been identified in APOGEE MEC/MBC/PXC (P2) (All versions < V...
same product
HIGH
CVE-2020-28388
A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions...
same product
MEDIUM
CVE-2021-31344
A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All ...
same product
MEDIUM
CVE-2021-31345
A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All ...
same product
HIGH
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Vendor Advisories
11siemens-csafSSA-223353
siemens-csafSSA-845392
siemens-csafSSA-620288
siemens-csafSSA-114589
siemens-csafSSA-044112
cisa-csafcisa-csaf-csaf_files-OT-white-2021-icsa-21-313-03
cisa-csafcisa-csaf-csaf_files-OT-white-2021-icsa-21-315-07
cisa-csafcisa-csaf-csaf_files-OT-white-2021-icsa-21-350-06
cisa-csafcisa-csaf-csaf_files-OT-white-2022-icsa-22-013-03
cisa-csafcisa-csaf-csaf_files-OT-white-2022-icsa-22-069-02
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References & Sources
10Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.