CVE-2019-5636 Beckhoff TwinCAT Discovery Service Denial of Service

What is CVE-2019-5636?

CVE-2019-5636 is a medium-severity denial of service vulnerability in Beckhoff TwinCAT 2, published on 21 Nov 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

When a Beckhoff TwinCAT Runtime receives a malformed UDP packet, the ADS Discovery Service shuts down. Note that the TwinCAT devices are still performing as normal. This issue affects TwinCAT 2 version 2304 (and prior) and TwinCAT 3.1 version 4204.0 (and prior).

Weakness: CWE-404

Which versions are affected by CVE-2019-5636?

It affects 1 product.

Products include Beckhoff Twincat.

How do I fix CVE-2019-5636?

No fix has been published for CVE-2019-5636 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-2019-5636 being exploited?

There is no known exploitation of CVE-2019-5636 in the wild and no public exploit code.

Other vulnerabilities in Beckhoff TwinCAT 2

• CVE-2019-16871 Auth bypass in n/a Critical 9.8
• CVE-2017-16726 Weak cryptography in Beckhoff TwinCAT Critical 9.1
• CVE-2018-7502 Privilege escalation in Beckhoff TwinCAT PLC products High 7.8
• CVE-2019-5637 Beckhoff TwinCAT Profinet Driver Divide-by-Zero Denial of Service High 7.5
• CVE-2017-16718 Weak cryptography in Beckhoff TwinCAT Medium 5.9

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-pv38-9q3c-3qq8.