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Vulnerability record · CVE-2021-27393 · published 22 April 2021

CVE-2021-27393: Siemens nucleus net vulnerability

Siemens · Nucleus Net

A vulnerability has been identified in Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2013.08), Nucleus Source Code (Versions including affected DNS modules). The DNS client does not properly randomize UDP port numbers of DNS requests. That could allow an attacker to poison the DNS cache or spoof DNS resolving.

5.3 CVSS 3.1 Medium EPSS 0.75% · top 46.8% CWE-330 · CWE-330
5.3CVSS 3.1 base score, v2 5.0
0.75%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

A vulnerability has been identified in Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2013.08), Nucleus Source Code (Versions including affected DNS modules). The DNS client does not properly randomize UDP port numbers of DNS requests. That could allow an attacker to poison the DNS cache or spoof DNS resolving.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cert-portal.siemens.com/productcert/pdf/ssa-201384.pdf Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-201384.pdf Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-27393), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.