Naravel
Subscribe

Narratives Security

Linux kernel CVE-2026-99999 lets VMs read host memory; fixes land

Linux Kernel

Built from 2 signals across 2 sources · 258 items reviewed

CVE-2026-99999 breaks a shared Linux kernel isolation boundary: specially crafted packets from a guest VM can read host memory, making the issue relevant beyond Vercel's sandboxes. Vercel confirmed the flaw after it was demonstrated against live sandboxes, while host code execution was shown only in lab testing and there is no evidence of real-world exploitation. Stable fixes are available across seven kernel branches.

  • The flaw is in skb_checksum_help(), where bad IPv4 checksum metadata can corrupt the network header and cause further impact.
  • A researcher demonstrated guest-to-host memory reads against Vercel's live cloud sandboxes; the issue is in Linux kernel networking code rather than a Vercel-specific configuration.
  • Host code execution was demonstrated only in lab tests, and there is no sign that CVE-2026-99999 has been used in a real attack.

Bottom line If you run Linux hosts for VMs or cloud sandboxes, upgrade to the corresponding fixed kernel release now and verify your guest-to-host isolation.

Signals2