CODESYS EtherNetIP - Improper timeout handling
CODESYS EtherNet/IP is an add‑on for the CODESYS Development System that provides a fully integrated EtherNet/IP protocol stack along with diagnostic capabilities. A flaw in the EtherNet/IP adapter protocol stack library results in a vulnerability within the generated application code. When an EtherNet/IP adapter is configured, this vulnerable protocol stack is downloaded to and executed by CODESYS Control runtime systems. Under certain non‑standard operating conditions, the EtherNet/IP adapter fails to perform timeout checks on active TCP connections. As a result, once all available TCP connections are in use, expired connections are not released and no new TCP connections can be established. Existing connections remain unaffected and continue to operate normally. This issue affects only CODESYS projects that include an EtherNet/IP adapter configuration.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-35225US | — | — | ||
An unauthenticated remote attacker is able to exhaust all available TCP connections in the CODESYS EtherNet/IP adapter stack, preventing legitimate clients from establishing new co… | ||||
references
External citations — patches, advisories, analysis.
- Advisory2026-04_VDE-2026-040: CODESYS EtherNetIP - Improper timeout handling - PDFself
- Advisory2026-04_VDE-2026-040: CODESYS EtherNetIP - Improper timeout handling - CSAFself
- Advisory2026-04_VDE-2026-040: CODESYS EtherNetIP - Improper timeout handling - HTMLself
- CERT@VDE Security Advisories for CODESYS GmbHexternal
- CODESYS Security Advisoriesexternal
remediations (1)
- FixedCODESYS EtherNetIP
Update the following products to version 4.9.0.0. * CODESYS EtherNetIP To make the fix effective for existing CODESYS projects, you must additionally update the EtherNet/IP adapter in the device tree to the latest version and perform a download of the CODESYS application to the PLC. The CODESYS Development System and the products available as CODESYS add-ons can be downloaded and installed directly with the CODESYS Installer or be downloaded from the CODESYS Store. Alternatively, as well as for all other products, you will find further information on obtaining the software update in the CODESYS Update area https://www.codesys.com/download/.
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