CVE-2021-21005

Name: CVE-2021-21005
Creator: NVD / NIST
Published: 2021-06-25T19:15:08.797+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.68%

Last modified Jun 17, 2026

CVE-2021-21005 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. In Phoenix Contact FL SWITCH SMCS series products in multiple versions if an attacker sends a hand-crafted TCP-Packet with the Urgent-Flag set and the Urgent-Pointer set to 0, the network stack will crash. The device needs to be rebooted afterwards.. EPSS estimates a 0.68% chance of exploitation in the next 30 days.

Description

In Phoenix Contact FL SWITCH SMCS series products in multiple versions if an attacker sends a hand-crafted TCP-Packet with the Urgent-Flag set and the Urgent-Pointer set to 0, the network stack will crash. The device needs to be rebooted afterwards.

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

0.68%

47.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-362

Affected Software

Vendor	Product	Versions
Phoenixcontact	Fl Switch Smcs 16tx Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 14tx\/2fx Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 14tx\/2fx-Sm Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 8gt Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 6gt\/2sfp Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 8tx-Pn Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 4tx-Pn Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 8tx Firmware	<= 4.70
Phoenixcontact	Fl Switch Smcs 6tx\/2sfp Firmware	<= 4.70
Phoenixcontact	Fl Switch Smn 6tx\/2pof-Pn Firmware	<= 4.70
Phoenixcontact	Fl Switch Smn 8tx-Pn Firmware	<= 4.70
Phoenixcontact	Fl Switch Smn 6tx\/2fx Firmware	<= 4.70
Phoenixcontact	Fl Switch Smn 6tx\/2fx Sm Firmware	<= 4.70
Phoenixcontact	Fl Nat Smn 8tx Firmware	<= 4.63
Phoenixcontact	Fl Nat Smn 8tx-M Firmware	<= 4.63

References

https://cert.vde.com/en-us/advisories/vde-2021-023Third Party Advisory
https://cert.vde.com/en-us/advisories/vde-2021-023Third Party Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2021-21005?

How severe is CVE-2021-21005?

CVE-2021-21005 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.68% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21005?

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-2021-21005?

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

Scan your code now

Source: NVD / NIST