CVE-2021-25677

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-04-22 · updated 2026-06-17
Weakness: CWE-330

Description

A vulnerability has been identified in APOGEE PXC Compact (BACnet) (All versions < V3.5.5), APOGEE PXC Compact (P2 Ethernet) (All versions < V2.8.20), APOGEE PXC Modular (BACnet) (All versions < V3.5.5), APOGEE PXC Modular (P2 Ethernet) (All versions < V2.8.20), Nucleus NET (All versions), Nucleus ReadyStart V3 (All versions < V2017.02.3), Nucleus ReadyStart V3 (All versions < V2017.02.4), Nucleus ReadyStart V4 (All versions < V4.1.0), Nucleus Source Code (Versions including affected DNS modules), SIMOTICS CONNECT 400 (All versions < V0.5.0.0), SIMOTICS CONNECT 400 (All versions >= V0.5.0.0 < V1.0.0.0), TALON TC Compact (BACnet) (All versions < V3.5.5), TALON TC Modular (BACnet) (All versions < V3.5.5). The DNS client does not properly randomize DNS transaction IDs. That could allow an attacker to poison the DNS cache or spoof DNS resolving.

Affected products

Siemens Nucleus NET: all versions
Siemens Nucleus ReadyStart V3: before 2017.02.4 — fixed in 2017.02.4
Siemens Nucleus ReadyStart V4: before 4.1.0 — fixed in 4.1.0
Siemens Nucleus Source Code: all versions
Siemens Simotics Connect 400 Firmware: from 0.5.0.0

How to fix

Upgrade to a fixed version: Siemens Nucleus ReadyStart V3 2017.02.4; Siemens Nucleus ReadyStart V4 4.1.0. Check the vendor advisory for mitigations.

References

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