VERCEL CONFIRMS KVM ZERO-DAY VM ESCAPE, AWARDS RESEARCHER $50,000

Summary from the TLDR InfoSec newsletter

A KVM zero-day reported by researcher Paulos Yibelo reportedly allowed guest code to gain root on the host, breaking the Firecracker microVM boundary Vercel Sandbox uses to isolate untrusted workloads and AI agents. Vercel CEO Guillermo Rauch confirmed the bug and that the $50,000 maximum bounty was awarded, but no CVE, affected kernel versions, exploit chain, or patch have been disclosed. Operators relying on KVM for multi-tenant isolation should watch for Vercel's promised write-up and Linux vendor advisories, and should not assume the unrelated Januscape fix covers this flaw.