A REVISIT OF REMOTE SPECTRE ATTACKS ON CLOUDFLARE WORKERS

Summary from the TLDR DevOps newsletter

Cloudflare researchers demonstrated a remote Spectre attack against its Workers production environment that reliably leaked up to 12 bits per second at 99% accuracy. The attack exploited a gap in Cloudflare's existing Dynamic Process Isolation defense, which only isolates suspicious scripts after an invocation ends, a delay attackers bypassed by keeping a single Durable Object invocation alive for hours via WebSocket messages. Cloudflare says no active exploitation was detected over the past three years. In response, the company has improved its isolation detection, integrated the V8 Sandbox, and deployed Memory Protection Keys to limit cross-isolate memory access within shared processes.