CVE-2021-21005: Phoenixcontact Fl Nat Smn 8tx-M Firmware

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

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.

Affected products

• Phoenixcontact Fl Nat Smn 8tx-M Firmware: up to and including 4.63
• Phoenixcontact Fl Nat Smn 8tx Firmware: up to and including 4.63
• Phoenixcontact Fl Switch Smcs 14tx/2fx-Sm Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 14tx/2fx Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 16tx Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 4tx-Pn Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 6gt/2sfp Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 6tx/2sfp Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 8gt Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 8tx-Pn Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smcs 8tx Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smn 6tx/2fx Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smn 6tx/2fx Sm Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smn 6tx/2pof-Pn Firmware: up to and including 4.70
• Phoenixcontact Fl Switch Smn 8tx-Pn Firmware: up to and including 4.70

Published 2021-06-25. Last modified 2026-06-17.