PHOENIX CONTACT: DoS for PLCnext Control devices in versions <2021.0.5 LTS

A device on the same network as the controller sending a special crafted JSON request to the /auth/access-token endpoint may cause the controller to restart (CWE-20).

UPDATE A

The CVSS score has been raised from 7.7 (CVSS:3.0:AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H) to 9.1 (CVSS:3.0:AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H)

An attacker could potentially script this request and create a denial of service attack condition.

Phoenix Contact recommends operating network-capable devices in closed networks or protected with a suitable firewall. For detailed information on our recommendations for measures to protect network-capable devices, please refer to our application note: Measures to protect network-capable devices with Ethernet connection

Phoenix Contact recommends affected users to upgrade to the current Firmware 2021.0.5 LTS or higher which fixes this vulnerability.