Cloudflare Workers Spectre Attack Leaks JWT From Co-Located Worker at 12 Bits/Second

Researchers have demonstrated a significant vulnerability in Cloudflare Workers, allowing a remote Spectre attack to leak JWTs from co-located Workers at a rate up to 12 bits per second. Despite previous mitigations like DyPrIs, the underlying detection approach remains insufficient, highlighting a fundamental limitation in how Cloudflare detects cross-isolate data leakage. Cloudflare has since deployed several hardening measures to address the issue.