A revisit of remote Spectre attacks on Cloudflare Workers

This post details a reassessment of remote Spectre attacks against Cloudflare Workers, identifying a limitation in the existing Dynamic Process Isolation (DyPrIs) defense. The research successfully demonstrated a remote Spectre attack in the production environment, leaking data at 12 bit/s with 99% accuracy. As a consequence, Cloudflare improved DyPrIs, integrated the V8 Sandbox, and added an in-process isolation mechanism to further mitigate memory disclosure attacks. The research also highlights the challenges of mounting such attacks in a production environment, including the need for a reliable remote timer and signal amplification techniques.