CVE-2021-25666

Brief service interruption via unthrottled ARP processing

Published Feb 9, 2021 · Updated Aug 3, 2024

Resource exhaustion in Siemens SCALANCE W780/W740 before 6.3 allows attackers to briefly disrupt device operation via ARP packets. The ARP-processing path allocates resources for specially crafted packets without limits or throttling, exhausting capacity needed for normal operation. Exploitation requires access to the device's local network segment and causes only a short-lived partial service interruption.

CVSS severity4.3
Medium
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Siemens SCALANCE W780/W740 before 6.3 allows attackers to briefly disrupt device operation via ARP packets. The ARP-processing path allocates resources for specially crafted packets without limits or throttling, exhausting capacity needed for normal operation. Exploitation requires access to the device's local network segment and causes only a short-lived partial service interruption.

The record

CVE
CVE-2021-25666
Published
Feb 9, 2021
Updated
Aug 3, 2024
Vendor
Siemens
Product
SCALANCE W780/W740
Classifications
CWE-770, T1498.001
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=All versions < V6.3

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Siemens · SCALANCE W780/W740version=All versions < V6.3

Published CVSS scores

3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P
4.3NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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-770Allocation of Resources Without Limits or Throttling
T1498.001Network Denial of Service: Direct Network Flood

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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