Cloudflare Workers Spectre Flaw Leaks Tenant JWT at 12 Bits Per Second

Researchers leak authentication tokens from co-located Cloudflare $NET Workers using remote Spectre attacks. The end-to-end attack extracted a JSON Web Token at 12 bits per second with 99.16% accuracy, 360 times faster than a 2021 test. The attack relied on WebSocket communications as a remote timer and exploited Durable Objects to keep isolates alive for up to 20 hours. Cloudflare patched the flaw using improved process isolation, V8 Sandbox integration, and Memory Protection Keys, reporting zero active exploitation over three years. "We demonstrate that the production implementation of DyPrIs was insufficient." — Research Team Trading off strict operating system boundaries for sub-millisecond cold starts will always leave multi-tenant runtimes vulnerable to the hardware physics they run on.