CODESYS Control V3 - NULL pointer dereference
A vulnerability in the CODESYS Control runtime system's CmpDevice component allows unauthenticated attackers to cause a denial-of-service (DoS) via specially crafted communication requests. The issue is triggered by a NULL pointer dereference and also affects systems when outdated CODESYS clients attempt to log in. Only PLCs based on the CODESYS Runtime Toolkit containing the components CmpDevice, CmpAuditLog, and CmpSessionInformation are impacted. **Update 1.1.0, 01.09.2025:** Updated remediation category - fixed SL runtimes are now available.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2025-41691US | — | — | ||
An unauthenticated remote attacker may trigger a NULL pointer dereference in the affected CODESYS Control runtime systems by sending specially crafted communication requests, poten… | ||||
references
External citations — patches, advisories, analysis.
- Advisory2025-08_VDE-2025-070: CODESYS Control V3 - NULL pointer dereference - HTMLself
- CERT@VDE Security Advisories for CODESYS GmbHexternal
- Advisory2025-08_VDE-2025-070: CODESYS Control V3 - NULL pointer dereference - PDFself
- Advisory2025-08_VDE-2025-070: CODESYS Control V3 - NULL pointer dereference - CSAFself
- CODESYS Security Advisoriesexternal
remediations (2)
- Mitigation
The vulnerability can be mitigated by restricting the allowed login authentication type "CmpUserMgr/UserLogin_AuthenticationType" to "ONLY_ASYMMETRIC". This can be configured either via the Device Security Settings dialog in the CODESYS Development System or directly in the configuration file of the CODESYS Control runtime system (CODESYSControl.cfg) by adding the following setting: [CmpUserMgr] SECURITY.UserLogin_AuthenticationType=ONLY_ASYMMETRIC With this configuration in place, both potential attackers and legacy CODESYS protocol clients (prior to version 3.5.16.0) will be blocked from logging in, thereby preventing execution of the vulnerable code path.
- Fixed
Update the following products to version 3.5.21.20. * CODESYS Control RTE (SL) * CODESYS Control RTE (for Beckhoff CX) SL * CODESYS Control Win (SL) * CODESYS HMI (SL) * CODESYS Runtime Toolkit 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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