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Vulnerability record · CVE-2021-25677 · published 22 April 2021

CVE-2021-25677: Siemens simotics connect 400 firmware vulnerability

Siemens · Simotics Connect 400 Firmware

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.

5.3 CVSS 3.1 Medium EPSS 1.1% · top 36.8% CWE-330 · CWE-330
5.3CVSS 3.1 base score, v2 5.0
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
5Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

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.

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

Affected products

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

References

LinkTags
https://cert-portal.siemens.com/productcert/pdf/ssa-180579.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-669158.pdf PatchVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-705111.pdf PatchVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-180579.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-669158.pdf PatchVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-705111.pdf PatchVendor 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-2021-25677), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.