ICS Advisories

Risk evaluation

A vulnerability has been identified in the CODESYS Control runtime system, which includes an abstraction layer designed to ensure compatibility across different operating systems. This layer is used both by affected CODESYS products and by applications running on the PLC. The platform-specific adaptation of this abstraction layer for Linux and QNX contains a flaw in the SysSocket implementation. Due to incorrect internal handling and depending on how the caller interacts with the affected function, the issue can lead to an out-of-bounds read. An unauthenticated attacker may be able to exploit this vulnerability via socket-based communication, potentially causing a crash of the corresponding communication task. Additionally, also clients such as the PLCHandler running on Linux or QNX may be affected if they connect to a malicious server that triggers the flaw. Successful exploitation requires the attacker to win a race condition, which increases the complexity of the attack. Note: All platforms other than Linux and QNX are not affected.

Mitigation summary

As the flaw resides in the SysSocketSelect() implementation, which has been switched to a poll()-based approach by default since version 3.5.21.0, the following setting can be added to the configuration file of the affected product (e.g., CODESYSControl.cfg) to revert to the select()-based implementation: [SysSocket] LinuxSelectPoll=1 Note: On Linux select() is limited to less than 1024 file descriptors.