CTFusion: A CTF-based Benchmark for LLM Agent Evaluation

Fuente: arXiv
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Main Authors: Lee, Dongjun, Bae, Ga-eun, Yun, Insu
Format: Preprint
Published: 2026
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author Lee, Dongjun
Bae, Ga-eun
Yun, Insu
author_facet Lee, Dongjun
Bae, Ga-eun
Yun, Insu
contents Recent advances in Large Language Models (LLMs) have enabled agentic systems for complex, multi-step tasks; cybersecurity is emerging as a prominent application. To evaluate such agents, researchers widely adopt Capture The Flag (CTF) benchmarks. However, current CTF benchmarks reuse existing challenges, which exposes them to data contamination and potential cheating. Notably, we confirmed these issues in practice by integrating web search tools into an existing agent. To address these limitations, we present CTFusion, a streaming evaluation framework built on Live CTFs. To achieve this, CTFusion preserves per-agent independence under a single team account and reduces competition impact by forwarding only the first correct flag per challenge. Moreover, we implement CTFusion as a Model Context Protocol (MCP) server on the widely used CTFd platform, which offers broad applicability to diverse CTF events and agent types. Through experiments with three LLMs, two agents, and five Live CTFs, we demonstrate that existing CTF benchmarks can be unreliable in assessing LLM-based agents, while CTFusion can serve as a robust solution for evaluating cybersecurity agents. We release CTFusion as open source to foster future research in this area.
format Preprint
id arxiv_https___arxiv_org_abs_2605_11504
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle CTFusion: A CTF-based Benchmark for LLM Agent Evaluation
Lee, Dongjun
Bae, Ga-eun
Yun, Insu
Machine Learning
Cryptography and Security
Recent advances in Large Language Models (LLMs) have enabled agentic systems for complex, multi-step tasks; cybersecurity is emerging as a prominent application. To evaluate such agents, researchers widely adopt Capture The Flag (CTF) benchmarks. However, current CTF benchmarks reuse existing challenges, which exposes them to data contamination and potential cheating. Notably, we confirmed these issues in practice by integrating web search tools into an existing agent. To address these limitations, we present CTFusion, a streaming evaluation framework built on Live CTFs. To achieve this, CTFusion preserves per-agent independence under a single team account and reduces competition impact by forwarding only the first correct flag per challenge. Moreover, we implement CTFusion as a Model Context Protocol (MCP) server on the widely used CTFd platform, which offers broad applicability to diverse CTF events and agent types. Through experiments with three LLMs, two agents, and five Live CTFs, we demonstrate that existing CTF benchmarks can be unreliable in assessing LLM-based agents, while CTFusion can serve as a robust solution for evaluating cybersecurity agents. We release CTFusion as open source to foster future research in this area.
title CTFusion: A CTF-based Benchmark for LLM Agent Evaluation
topic Machine Learning
Cryptography and Security
url https://arxiv.org/abs/2605.11504