WAGO: PLC families 750-88x and 750-352 prone to DoS attack, versions < FW10 (Update A)

Old versions of the firmware (FW1 to FW10) are prone to a DoS attack. Firmware versions > FW11 (released in Dec, 2017) are not affected.

VDE-2020-042 (2020-10-27 12:28 UTC+0200)

CVE Identifier

CVE-2020-12516

Severity

7.5 (CVSS:3.1:AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Affected Vendors

WAGO

Affected Products

750-352
750-831/xxx-xxx
750-852
750-880/xxx-xxx
750-881
750-889

UPDATE A:

750-331/xxx-xxx
750-829
750-882
750-885

END UPDATE A

Firmware versions from FW1 to FW10 are affected. All newer Firmware releases since FW11, released in December 2017, are not affected.

Vulnerability Type

Uncontrolled Resource Consumption (CWE-400)

Summary

The Web-Based Management (WBM) of WAGOs programmable logic controller (PLC) is typically used for administration, commissioning and updates.
Older firmware versions of the PLC family 750-88x and 750-352 are vulnerable for a special denial of service attack.

Impact

An attacker which sends a series of maliciously constructed packets to HTTP(S) ports 80/443 could cause a crashed device, that needs a power on reset to go back to normal operation.

Solution

Update the device to the latest FW version available here: https://www.wago.com/us/requestDownload?downloadFile=FWMedia_58_750-881

Mitigation

Restrict network access to the device.
Do not directly connect the device to the internet
Disable unused TCP/UDP-ports

Reported by

This vulnerability was reported to WAGO by William Knowles (Applied Risk)

CERT@VDE coordinated.