CVE-2021-27393: Siemens Nucleus Net

Medium severity, CVSS 5.3. EPSS: 0.8% chance of exploitation in the next 30 days.

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.

Affected products

• Siemens Nucleus Net: any version
• Siemens Nucleus Readystart v3: before 2013.08 (fixed in 2013.08)
• Siemens Nucleus Source Code: affected versions not specified

Published 2021-04-22. Last modified 2026-06-17.