CVE-2020-12521: Phoenix Contact PLCnext Control Devices versions before 2021.0 LTS: A specially crafted LLDP packet may lead to a high system load in the PROFINET stack.

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-12-17 · updated 2026-06-17
Weakness: CWE-20

Description

On Phoenix Contact PLCnext Control Devices versions before 2021.0 LTS a specially crafted LLDP packet may lead to a high system load in the PROFINET stack. An attacker can cause failure of system services or a complete reboot.

Affected products

Phoenixcontact Plcnext Firmware: before 2021.0 — fixed in 2021.0

How to fix

Upgrade to a fixed version: Phoenixcontact Plcnext Firmware 2021.0. Check the vendor advisory for mitigations.

References

https://cert.vde.com/en-us/advisories/vde-2020-049
https://cert.vde.com/en-us/advisories/vde-2020-049

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