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Towards Knowledge Graph-Grounded Evaluation of Agentic LLMs on Cybersecurity Capture-the-Flag Challenges

Paper · 2026 · Daniel Schlör, Marius Bohn, Maximilian Wolf et al.

Summary

Agentic LLMs for offensive security are usually scored on whether they capture the flag, or against ad hoc checkpoints defined per challenge. These methods say little about partial progress or about valid alternative solutions. The authors address this with BraceGreen, which turns human-written CTF writeups into knowledge graphs that serve as gold-standard rubrics.

Each attack step is a node tagged with:

  • a MITRE ATT&CK tactic
  • a natural-language goal
  • a reference command and its expected output
  • a semantic result

Edges capture attack order, equivalent alternative commands or multi-command workflows, data-flow prerequisites, and conditions that make a command a poor choice.

A LangGraph workflow uses an LLM-as-judge with chain-of-thought reasoning. The judge checks an agent's prediction against every alternative the graph encodes, not just one reference answer.

The released resource covers seven VulnHub machines and connects to live targets through virtual machines and an MCP server. The excerpt contains no quantitative evaluation results. Its main value is a standardized, reproducible schema for fine-grained, step-level assessment of security agents, independent of the agent framework used.

Key points

  • Benchmark: 7 VulnHub CTF machines with full knowledge graph annotations, released at github.com/LSX-UniWue/brace-ctf-data.
  • Graph schema: RDF-compatible, with three node types (Step, Command, Command group).
    • Structural edges: next_step, or and has_subcmd.
    • Relations: has_tactic, has_goal, has_cmd, has_output, has_result, requires, contraindicated_by and is_optional.
  • Tactic coverage: steps map to 10 MITRE ATT&CK tactic categories, from Reconnaissance and Discovery through Privilege Escalation, Lateral Movement and Command and Control.
  • Evaluation modes: three modes (command prediction, goal inference, anticipated result), each scored by an LLM-as-judge inside a LangGraph pipeline.
  • Positioning: unlike binary benchmarks (NYU CTF Bench), milestone-based ones (AutoPenBench, Cybench) or rubric trees (PentestJudge), BraceGreen encodes alternative solution paths and prerequisites explicitly. It is limited to technical attack steps.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

Also on the byline: Coburg University of Applied Sciences.

 Fields, topics and concepts

Cite

Cite as Daniel Schlör, Marius Bohn, Maximilian Wolf, Kevin Bergner, Christian Goldschmied and Andreas Hotho. 2026. Towards Knowledge Graph-Grounded Evaluation of Agentic LLMs on Cybersecurity Capture-the-Flag Challenges. Proceedings of the Knowledge Graphs and Large Language Models Workshop (KG-LLM) @ LREC26.

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.63317/4ne74wm45iti

@inproceedings{schlor2026knowledge,
  title = {{Towards Knowledge Graph-Grounded Evaluation of Agentic LLMs on Cybersecurity Capture-the-Flag Challenges}},
  author = {Daniel Schlör, Marius Bohn, Maximilian Wolf, Kevin Bergner, Christian Goldschmied and Andreas Hotho},
  booktitle = {Proceedings of the Knowledge Graphs and Large Language Models Workshop (KG-LLM) @ LREC26},
  year = {2026},
  doi = {10.63317/4ne74wm45iti},
  url = {https://doi.org/10.63317/4ne74wm45iti}
}

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