CVE-2021-21002

Name: CVE-2021-21002
Creator: NVD / NIST
Published: 2021-06-25T19:15:08.587+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.96%

Last modified Jun 17, 2026

CVE-2021-21002 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In Phoenix Contact FL COMSERVER UNI in versions < 2.40 a invalid Modbus exception response can lead to a temporary denial of service.. EPSS estimates a 0.96% chance of exploitation in the next 30 days.

Description

In Phoenix Contact FL COMSERVER UNI in versions < 2.40 a invalid Modbus exception response can lead to a temporary denial of service.

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

0.96%

57.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-772

Affected Software

Vendor	Product	Versions
Phoenixcontact	Fl Comserver Uni 232\/422\/485 Firmware	< 2.40
Phoenixcontact	Fl Comserver Uni 232\/422\/485-T Firmware	< 2.40

References

https://cert.vde.com/en-us/advisories/vde-2021-022Third Party Advisory
https://cert.vde.com/en-us/advisories/vde-2021-022Third Party Advisory

Timeline

Published: Jun 25, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21002?

In Phoenix Contact FL COMSERVER UNI in versions < 2.40 a invalid Modbus exception response can lead to a temporary denial of service.

How severe is CVE-2021-21002?

CVE-2021-21002 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.96% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21002?

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-2021-21002?

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

Scan your code now

Source: NVD / NIST