CVE-2021-25659Network attack vector

Remote service interruption via crafted packets

Published Aug 10, 2021 · Updated Aug 3, 2024

Resource exhaustion in Siemens Automation License Manager 5 and 6 before 6.0 SP9 Update 2 allows remote attackers to interrupt service. The TCP/4410 service processes specially crafted packets without bounding memory consumption, exhausting memory needed for legitimate operation. An unauthenticated attacker needs network access to the listening service; exploitation prevents legitimate use but has no reported data impact.

CVSS severity7.5
High
EPSS probability1.04%
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 Automation License Manager 5 and 6 before 6.0 SP9 Update 2 allows remote attackers to interrupt service. The TCP/4410 service processes specially crafted packets without bounding memory consumption, exhausting memory needed for legitimate operation. An unauthenticated attacker needs network access to the listening service; exploitation prevents legitimate use but has no reported data impact.

The record

CVE
CVE-2021-25659
Published
Aug 10, 2021
Updated
Aug 3, 2024
Vendor
Siemens
Product
Automation License Manager
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 10, 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
  2. Affected versionversion=All versions < V6.0 SP9 Update 2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Siemens · Automation License Managerversion=All versions; version=All versions < V6.0 SP9 Update 2

Published CVSS scores

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion 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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