CVE-2020-12523: Phoenixcontact Fl Mguard RS4004 Tx/dtx Firmware

Critical severity, CVSS 9.1. EPSS: 0.9% chance of exploitation in the next 30 days.

On Phoenix Contact mGuard Devices versions before 8.8.3 LAN ports get functional after reboot even if they are disabled in the device configuration. For mGuard devices with integrated switch on the LAN side, single switch ports can be disabled by device configuration. After a reboot these ports get functional independent from their configuration setting: Missing Initialization of Resource

Affected products

• Phoenixcontact Fl Mguard RS4004 Tx/dtx Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Fl Mguard RS4004 Tx/dtx VPN Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Innominate Mguard RS4000 4tx/3g/tx VPN Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Innominate Mguard RS4000 4tx/tx Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Innominate Mguard RS4000 4tx/tx VPN Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Tc Mguard RS4000 3g VPN Firmware: affected versions not specified
• Phoenixcontact Tc Mguard RS4000 4g Att VPN Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Tc Mguard RS4000 4g VPN Firmware: before 8.8.3 (fixed in 8.8.3)
• Phoenixcontact Tc Mguard RS4000 4g Vzw VPN Firmware: before 8.8.3 (fixed in 8.8.3)

Published 2020-12-17. Last modified 2026-06-17.