$536 and 8 Hours: AI Learns to Attack a Different PLC

Experts got Claude to port a PLC exploit, but it cost $536 and 8 hours, and a later AI-generated payload accidentally destroyed the hardware.

Forescout researchers just answered a question that’s been hanging over industrial security for a while: can AI actually port a working exploit from one PLC to a different model with no source code and no debugger access? Their report says yes, but the answer comes with a price tag, a lot of researcher hand-holding, and a permanently destroyed piece of hardware.

The starting point was CVE-2021-31886, a pre-authentication buffer overflow in the Nucleus FTP server that the team had already exploited on a WAGO 750-852 PLC in earlier research. The goal this time was porting that working exploit to a related but distinct model, the WAGO 750-831, using Claude Code with access to a terminal, Ghidra, and the actual physical device.

“The exploit depended on target-specific parameters, including function addresses, offsets, and memory locations. Our goal was to use AI to port the exploit to a similar, but not identical PLC model: the WAGO 750-831. Beyond simply porting the existing RCE, we also wanted to test whether AI could help extend it into a more capable command-and-control implant on the constrained PLC.” reads the report. “We began this research with three inputs:

• The working RCE exploit for the WAGO 750-852 PLC.
• A firmware binary file for the other PLC, the WAGO 750-831 (V01.04.16), which the original security advisory flagged as vulnerable.
• A physical WAGO 750-831 PLC running that firmware.”

This was a much harder task than the software exploits AI has handled before. Working with embedded firmware is difficult when there’s no source code and no debugger to help explain what’s happening.

Finding the vulnerability took a few attempts, but it wasn’t the hardest part. Claude tested the live FTP server, analyzed the firmware with Ghidra and wrote its own Python scripts to help with the analysis. It eventually crashed the PLC, confirming that the buffer overflow could be triggered.

The real challenge was going from a crash to actually running attacker-controlled code. That required much more work, and progress slowed down at that point.

The turning point came when Claude figured out why its injected shellcode kept disappearing before it could run. Normal FTP command processing was zeroing out the exact memory buffer holding the malicious payload right after the login command completed, and the fix meant deliberately avoiding that normal completion path entirely.

“Claude determined that the exploit path could preserve the shellcode by avoiding the normal command-completion path. Omitting the ‘\r\n’ (CRLF) terminator prevented the relevant processing path from completing in the usual way, leaving the attacker-controlled buffer intact.” continues the report. “Claude then created a test harness that measured PLC uptime after each exploit attempt. The device consistently crashed at the same point regardless of the injected payload, indicating that execution was failing before the payload itself could influence the outcome. This supported the hypothesis that the shellcode was being overwritten during normal FTP processing rather than executed.”

Claude got there with heavy guidance but got there nonetheless.

Once Claude solved that specific problem, things moved much faster. In just 12 minutes, it went from a harmless test payload to two working exploits: one made the PLC send ICMP pings to a remote machine, while the other sent a UDP packet containing the word “PWNED.”

Most of the time and effort went into solving the target-specific issue that was preventing the payload from running. After that, generating the working exploits was relatively easy.

The process still required a lot of time and money. The final exploit-development stage cost $535.74 in API fees during an 8-hour, 32-minute session, and the researchers had to guide Claude through several dead ends, provide disassembly details and switch to a larger context model when the smaller sessions ran out of space.

“The final RCE development stage consumed $535.74 in API usage, based on 2.6k input tokens and 1.3M output tokens. The corresponding session lasted 8 hours, 32 minutes, spread across several days of research. Most of that time was spent identifying the buffer-preservation issue associated with the FTP command-processing path.” states the report. “After achieving the initial RCE, we opened a new Claude Opus 4.6 session to explore whether the working ICMP and UDP payloads could be extended into a command-and-control implant. The prompt began: “I have working PoCs for UDP and ICMP beacons, read them and let’s plan a C2 implant on the PLC”.”

So, for now, this isn’t something an inexperienced attacker can simply hand to an AI and expect to work. It still takes expert guidance, substantial time and a not-so-small bill.

The most telling moment of the whole exercise happened after the exploit already worked. Researchers asked Claude to extend the working ICMP and UDP payloads into a full command-and-control implant, and while probing the PLC’s memory layout to build that, one generated payload wrote to a region mapped to flash storage, permanently bricking the device. Nobody told Claude to break anything; it was doing exactly what it was asked and still destroyed the hardware in the process, which is a genuinely unsettling data point for anyone imagining more autonomous AI agents operating against real physical infrastructure with less supervision.

The biggest finding here may not be that Claude successfully ported the exploit, but how fragile the process still is. Forescout also points to real incidents where attackers disrupted U.S. water utilities by abusing internet-exposed PLCs directly, without needing a sophisticated exploit.

That should still concern defenders. If AI keeps reducing the time, cost and expertise needed to develop more advanced attacks against PLCs, the idea that industrial systems are simply too difficult to hack may not hold for much longer. For now, the research shows that AI still needs expert guidance, but that gap could narrow as the technology improves.

“Recent attacks against internet-facing PLCs show that exposed controllers already create operational risk, even without the kind of RCE developed in this research. The concern is that AI could make more sophisticated exploitation easier to reproduce across those exposed devices. Today, that still requires specialist knowledge and time. But if AI continues to reduce both, vulnerabilities that once looked too difficult or uneconomical to exploit may deserve a different level of attention.” concludes the report. “For critical infrastructure organizations, the immediate implication is simple: do not dismiss vulnerabilities on OT devices merely because exploitation appears difficult today.”

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Pierluigi Paganini

(SecurityAffairs – hacking, PLC exploit)