Vercel Bug Bounty Uncovers Linux Flaws Threatening Cloud Isolation

Vercel’s two-week sandbox bug-bounty challenge generated 1,285 reports from HackerOne researchers conducting black-box testing and Trail of Bits engineers performing white-box assessments. The programme ran from 18 August to 1 September with a $1 million reward pot. Vercel said that, while triage will continue until 1 October, it has so far validated one Critical, seven High, 15 Medium, 49 Low and 19 Informative findings, with about $325,000 in payouts committed. None of the reports demonstrated access to real customer data.

The most significant discovery involved two independent defects in the Linux kernel networking stack, rather than in Vercel’s own code. One can leak memory from the host kernel, while the other can deterministically crash the host. Vercel said the issues may affect other cloud services that use the same Linux isolation layer, and that it alerted kernel maintainers two weeks before publication. Fixes are under private review and CVEs are pending, so technical details have not yet been released.

Trail of Bits submitted 20 findings and recommended architectural changes, including treating values returned by code inside microVMs as tenant-controlled input rather than trusting them.

The volume of submissions also led Vercel to build an AI-assisted triage agent that checks policy, identifies duplicates, retrieves source code and runs proof-of-concept exploits in a real sandbox. The company plans to open-source the agent, which runs on Kimi K3. Vercel described the challenge as strengthening its sandbox, but the results do not establish that the system is free of undiscovered vulnerabilities.