Vercel announces results of the $1M Sandbox challenge: 1,285 reports, a kernel zero-day, no evidence of customer data being read

Vercel announced the results of its $1 million Vercel Sandbox escape challenge, receiving 1,285 reports in two weeks and paying $242,000 in bounties. The most severe issue was a zero-day vulnerability in the Linux kernel network stack. Researcher Paulos Yibelo sent specially crafted packets from within a microVM, which could leak host memory to the network, crash the host, and execute code on the host with administrator privileges. Vercel said it worked with vendors such as AWS to prioritize fixes; the patch is still under private review and a CVE is pending. A Vercel intern also discovered a cross-tenant data leak in the device-mapper storage layer that could read recycled disk blocks from deleted sandboxes. Trail of Bits submitted 20 findings over four engineer-weeks, concluded that the virtualization boundary is reliable, and proposed three structural recommendations that have been implemented. Vercel said no reports indicated customer data was read.