How severe is CVE-2021-25659?

CVE-2021-25659 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-25659 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25659?

CVE-2021-25659 affects Siemens Automation License Manager. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-25659?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-25659 published?

CVE-2021-25659 was published on 2021-08-10 and last updated on 2026-06-17.

CVE-2021-25659

CVE-2021-25659 is a high-severity vulnerability in Siemens Automation License Manager with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Siemens Automation License Manager
Published: 2021-08-10
Last modified: 2026-06-17

Description

A vulnerability has been identified in Automation License Manager 5 (All versions), Automation License Manager 6 (All versions < V6.0 SP9 Update 2). Sending specially crafted packets to port 4410/tcp of an affected system could lead to extensive memory being consumed and as such could cause a denial-of-service preventing legitimate users from using the system.

Frequently asked questions

What is CVE-2021-25659?: A vulnerability has been identified in Automation License Manager 5 (All versions), Automation License Manager 6 (All versions < V6.0 SP9 Update 2). Sending specially crafted packets to port 4410/tcp of an affected system could lead to extensive memory being consumed and as such could cause a denial-of-service preventing legitimate users from using the system.
How severe is CVE-2021-25659?: CVE-2021-25659 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-25659 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-25659?: CVE-2021-25659 affects Siemens Automation License Manager. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-25659?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-25659 published?: CVE-2021-25659 was published on 2021-08-10 and last updated on 2026-06-17.

References

https://cert-portal.siemens.com/productcert/pdf/ssa-158827.pdf

Affected products (1)

cpe:2.3:a:siemens:automation_license_manager:*:*:*:*:*:*:*:*

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