UK AISI and US CAISI: Kimi K3 Scores 32% on ExploitBench vs 76% for Top US Models, With No Working Safeguards

NIST / UK AISI / Hacker News·high signal

The UK AI Security Institute and the US Center for AI Standards and Innovation published a joint preliminary cyber evaluation of Moonshot AI's Kimi K3 (released July 16, open weights due July 27). On ExploitBench — a Carnegie Mellon benchmark covering 41 post-2023 Chrome V8 vulnerabilities — K3 scored 32% against 76% for the most cyber-capable US models, and achieved arbitrary code execution on 0 of 41 samples versus 20 of 41 for frontier models. It reached step 17 of a 32-step simulated network attack versus 28.5 for leading models, but crucially the institutes found K3's safeguards 'did not prevent it from attempting cyber exploit development or offensive cyber operations.'