Claude AI Builds Pre-Auth RCE Exploit for WAGO PLC to Execute ARM Shellcode Without Credentials

Researchers used Claude AI to help port a pre-authentication remote code execution exploit to a WAGO programmable logic controller, demonstrating how AI can assist with low-level operational technology exploitation.

The experiment achieved arbitrary ARM shellcode execution on a WAGO 750-831 PLC without valid credentials. However, it required major human involvement, expensive API usage, and eventually bricked the test device.

The exploit targeted CVE-2021-31886, a buffer overflow affecting the Nucleus FTP server used in several embedded products. The flaw exists because the FTP service fails to validate the length of a username submitted through the USER command.

A specially crafted oversized username can overwrite memory and redirect program execution. Forescout researchers focused on a WAGO 750-831 PLC running firmware V01. 04. 16. Researchers already had a working exploit for the related WAGO 750-852 model.

Claude AI Builds Pre-Auth RCE Exploit for WAGO PLC

They used Claude to identify the new device’s target-specific memory addresses, function offsets, callback locations, and shellcode storage regions.

Unlike conventional web or application exploitation, the PLC test involved a closed-source embedded device with no access to a debugger.

Claude Code used firmware analysis tools, Ghidra , generated Python scripts, and network testing utilities to inspect the firmware and interact with the live controller.

However, the AI initially followed incorrect code paths, generated invalid exploit attempts, and required researchers to provide disassembly details and steer the analysis.

ICMP beacon exploit (source: Forescout)

The first successful result was a crash, confirming that the overflow could be triggered. Achieving reliable RCE proved much harder.

A new demonstration shows that an AI-assisted workflow can port a pre-authentication remote code execution exploit to a vulnerable WAGO programmable logic controller, allowing arbitrary ARM shellcode to run without valid credentials.

The research documented by Forescout shows meaningful progress in AI-enabled exploitation of operational technology but also reveals that the process remains expensive, error-prone, and heavily dependent on human reverse-engineering expertise.

The experiment targeted CVE-2021-31886, a buffer-overflow vulnerability in the Nucleus FTP server used by certain embedded systems, including affected WAGO PLCs.

Claude AI Creates Pre-Auth RCE Exploit for WAGO PLC

The flaw occurs because the FTP service fails to adequately validate the length of a username supplied through the USER command. An attacker able to reach the vulnerable FTP service could use an oversized username to overwrite memory.

In Forescout’s test, that capability resulted in arbitrary ARM shellcode executing on a WAGO 750-831 PLC running firmware version V01. 04. 16. The proof of concept required no FTP authentication because the vulnerable processing occurs before login.

The successful payloads reportedly executed in the PLC’s Ethernet receive callback context, causing the device to generate outbound ICMP echo requests and UDP packets containing a test message.

Forescout began with an existing exploit for a related WAGO 750-852 model, then tasked Claude Code with adapting it to the 750-831. The AI had access to the target firmware, a live PLC, Ghidra, Python, terminal tools, and the reference exploit.

Claude initially identified an apparently separate potential vulnerability in the firmware’s FTP parsing logic, but researchers redirected the work toward the known CVE-2021-31886 flaw.