CVE-2021-33720

Name: CVE-2021-33720
Creator: NVD / NIST
Published: 2021-09-14T11:15:24.54+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.00%

Last modified Jun 17, 2026

CVE-2021-33720 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP100 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP300 (All versions < V8.80). Specially crafted packets sent to port 4443/tcp could cause a Denial-of-Service condition.. EPSS estimates a 1.00% chance of exploitation in the next 30 days.

Description

A vulnerability has been identified in SIPROTEC 5 relays with CPU variants CP050 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP100 (All versions < V8.80), SIPROTEC 5 relays with CPU variants CP300 (All versions < V8.80). Specially crafted packets sent to port 4443/tcp could cause a Denial-of-Service condition.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.00%

58.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Siemens	Siprotec 5 With Cpu Variant Cp050	< 8.80
Siemens	Siprotec 5 With Cpu Variant Cp100	< 8.80
Siemens	Siprotec 5 With Cpu Variant Cp300	< 8.80

References

https://cert-portal.siemens.com/productcert/pdf/ssa-847986.pdfPatch, Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-847986.pdfPatch, Vendor Advisory

Timeline

Published: Sep 14, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-33720?

How severe is CVE-2021-33720?

CVE-2021-33720 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.00% probability of exploitation in the next 30 days.

How do I fix CVE-2021-33720?

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-2021-33720?

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

Scan your code now

Source: NVD / NIST