CVE-2026-76992: Uncontrolled Memory Allocation in CODESYS Gateway Client

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-30 · updated 2026-09-30
Weakness: CWE-770

Description

The CODESYS Gateway Client allocates memory based on a size field in a gateway response without enforcing an appropriate upper limit. An unauthenticated remote attacker controlling a malicious gateway can exploit this behavior to trigger excessive memory consumption, resulting in a denial-of-service condition thus leading to a total loss of availablity.

Affected products

CODESYS Development System 3: from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40
CODESYS Edge Gateway for Linux: from 3.15.0.0 before 4.23.0.0 — fixed in 4.23.0.0
CODESYS Edge Gateway for Windows: from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40
CODESYS Gateway Server V2: from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40
CODESYS HMI (SL): from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40
CODESYS OPC DA Server SL: from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40
CODESYS PLCHandler: from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40
CODESYS Runtime Toolkit: from 3.0.0.0 before 3.5.22.40 — fixed in 3.5.22.40

How to fix

Upgrade to a fixed version: CODESYS Development System 3 3.5.22.40; CODESYS Edge Gateway for Linux 4.23.0.0; CODESYS Edge Gateway for Windows 3.5.22.40; CODESYS Gateway Server V2 3.5.22.40; CODESYS HMI (SL) 3.5.22.40; CODESYS OPC DA Server SL 3.5.22.40; CODESYS PLCHandler 3.5.22.40; CODESYS Runtime Toolkit 3.5.22.40. Check the vendor advisory for mitigations.

References

https://www.certvde.com/en/advisories/VDE-2026-094/

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