CVE-2021-47770: RCE in OpenPLC v3

Successful exploitation of CVE-2021-47770 allows an attacker with valid credentials to upload a custom hardware layer containing embedded reverse shell code. This code establishes a network connection to a specified IP address and port, effectively providing the attacker with a remote command execution shell on the PLC. The potential impact is severe, as an attacker could manipulate industrial processes, steal sensitive data, or disrupt operations. Given the nature of PLCs in critical infrastructure and industrial control systems, this vulnerability poses a significant risk of widespread operational disruption and potential safety hazards. The ability to remotely execute commands bypasses standard security controls, making it a particularly dangerous threat.

1. Reserved2026-01-14
2. Published2026-01-21
3. Modified2026-04-07
4. EPSS updated2026-03-23

The primary mitigation for CVE-2021-47770 is to upgrade OpenPLC to version 3.1.0 or later, which contains the fix. If an immediate upgrade is not feasible, consider implementing stricter access controls to the hardware configuration interface, limiting access to only authorized personnel. Network segmentation can also help to isolate the PLC from other systems, limiting the potential blast radius of a successful attack. Monitor network traffic for unusual connections originating from the PLC, particularly connections to external IP addresses and ports. Review and audit existing hardware configurations for any signs of tampering.