CVE-2021-31890Network attack vector

Device service interruption via unchecked TCP payload length

Published Nov 9, 2021 · Updated Mar 11, 2025

Improper TCP length handling in Siemens Capital Embedded AR Classic, PLUSCONTROL, and SIMOTICS CONNECT 400 allows remote attackers to interrupt service. The Nucleus NET TCP/IP stack accepts the total TCP payload length from the IP header without checking consistency with the available network buffer. No authentication or user interaction is required; crafted traffic can interrupt service, while Siemens limits the scored impact to availability.

CVSS severity7.5
High
EPSS probability2.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper TCP length handling in Siemens Capital Embedded AR Classic, PLUSCONTROL, and SIMOTICS CONNECT 400 allows remote attackers to interrupt service. The Nucleus NET TCP/IP stack accepts the total TCP payload length from the IP header without checking consistency with the available network buffer. No authentication or user interaction is required; crafted traffic can interrupt service, while Siemens limits the scored impact to availability.

The record

CVE
CVE-2021-31890
Published
Nov 9, 2021
Updated
Mar 11, 2025
Vendor
Siemens
Product
Capital Embedded AR Classic
Classifications
CWE-240, T0814
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <*
  2. Affected versionversion=0 <V2303

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · Capital Embedded AR Classicversion=0 <*; version=0 <V2303
Siemens · PLUSCONTROL 1st Genversion=All versions
Siemens · SIMOTICS CONNECT 400version=All versions < V0.5.0.0; version=All versions < V1.0.0.0

Published CVSS scores

7.5Siemens AGCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-240Improper Handling of Inconsistent Structural Elements
T0814Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo