CVE-2021-31883

ECU service interruption via malformed DHCP ACK

Published Nov 9, 2021 · Updated Mar 11, 2025

Denial of service in Siemens Capital Embedded AR Classic 431-422 and R20-11 before 2303 allows attackers to interrupt DHCP clients. Its Nucleus NET DHCP client processes Vendor options in DHCP ACK packets without validating their encoded length against the available option data. Exploitation requires enabled DHCP client functionality and adjacent-network access; Siemens does not specify whether the resulting interruption is a hang, crash, or reboot.

CVSS severity7.1
High
EPSS probability1.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Siemens Capital Embedded AR Classic 431-422 and R20-11 before 2303 allows attackers to interrupt DHCP clients. Its Nucleus NET DHCP client processes Vendor options in DHCP ACK packets without validating their encoded length against the available option data. Exploitation requires enabled DHCP client functionality and adjacent-network access; Siemens does not specify whether the resulting interruption is a hang, crash, or reboot.

The record

CVE
CVE-2021-31883
Published
Nov 9, 2021
Updated
Mar 11, 2025
Vendor
Siemens
Product
Capital Embedded AR Classic
Classifications
CWE-119, T1499
Attack vector
adjacent
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

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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 vectoradjacent
Required privilegesunauthenticated

What is affected?

Siemens · Capital Embedded AR Classicversion=0 <*; version=0 <V2303

Published CVSS scores

7.1Siemens AGCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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