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Exploit Evals \ red.anthropic.com

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Claude Mythos Preview’s ability to develop exploits is a step-change over previous frontier models. This was one of our primary motivations for rolling out the model carefully through Project Glasswing rather than through a general release. Mythos Preview is capable of finding complex vulnerabilities, but what concerned us most in our internal testing was that Mythos Preview could both turn vulnerabilities into exploit primitives, and combine those primitives together into complete end-to-end attack chains. When we published our Mythos Preview results, we measured its capabilities by having it search for novel zero-days and then build exploits for them. Qualitative evaluations like this are helpful for showcasing a model’s capabilities—but ideally, we would have high-quality quantitative benchmarks that let us measure them precisely. The problem we faced at the time we released Mythos Preview was that no existing public exploit benchmarks were difficult enough to capture Mythos Preview

Frontier Red Team Measuring LLMs’ ability to develop exploits May 22, 2026 Newton Cheng, Keane Lucas, Winnie Xiao, Nicholas Carlini, and Milad Nasr Introduction Claude Mythos Preview ’s ability to develop exploits is a step-change over previous frontier models. This was one of our primary motivations for rolling out the model carefully through Project Glasswing rather than through a general release. Mythos Preview is capable of finding complex vulnerabilities, but what concerned us most in our internal testing was that Mythos Preview could both turn vulnerabilities into exploit primitives, and

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