CVE-2018-7821 Denial of service in SoMachine Basic and Modicon M221, SoMachine Basic, all versions Modicon M221, all references, all versions prior to firmware V1.10.0.0

High 7.5 Published 22 May 2019 Updated 29 May 2026

Flooding the Ethernet interface of Modicon M221 PLCs with active Ethernet/IP adapter causes cycle time impact, leading to denial of service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2018-7821?

CVE-2018-7821 is a high-severity denial of service vulnerability in SoMachine Basic and Modicon M221, SoMachine Basic, all versions Modicon M221, all references, all versions prior to firmware V1.10.0.0, published on 22 May 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

An Environment (CWE-2) vulnerability exists in SoMachine Basic, all versions, and Modicon M221(all references, all versions prior to firmware V1.10.0.0) which could cause cycle time impact when flooding the M221 ethernet interface while the Ethernet/IP adapter is activated.

Weakness: CWE-770, CWE-400

Which versions are affected by CVE-2018-7821?

It affects 2 products.

Products include Schneider-Electric Modicon M221 Firmware, Schneider-Electric Somachine Basic.

How do I fix CVE-2018-7821?

No fix has been published for CVE-2018-7821 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2018-7821 being exploited?

There is no known exploitation of CVE-2018-7821 in the wild and no public exploit code.

Sources

Also known as GHSA-cr3f-ppw7-pmqf.