CVE-2021-25677

Name: CVE-2021-25677
Creator: NVD / NIST
Published: 2021-04-22T21:15:10.207+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.3/10EPSS 1.06%

Last modified Jun 17, 2026

CVE-2021-25677 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. 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. EPSS estimates a 1.06% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

5.3/10

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

EPSS Probability

1.06%

60.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Siemens	Simotics Connect 400 Firmware	>= 0.5.0.0
Siemens	Nucleus Net	All versions
Siemens	Nucleus Readystart V3	< 2017.02.4
Siemens	Nucleus Readystart V4	< 4.1.0
Siemens	Nucleus Source Code	All versions

References

https://cert-portal.siemens.com/productcert/pdf/ssa-180579.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-669158.pdfPatch, Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-705111.pdfPatch, Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-180579.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-669158.pdfPatch, Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-705111.pdfPatch, Vendor Advisory

Timeline

Published: Apr 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-25677?

How severe is CVE-2021-25677?

CVE-2021-25677 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 1.06% probability of exploitation in the next 30 days.

How do I fix CVE-2021-25677?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-25677?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST