PwnEscape, CVE-2026-99999, can break isolation when the host Linux network stack fails to validate malformed checksum metadata sent by a guest. Host-memory exposure was observed in Vercel production sandboxes, while researchers reproduced host crashes and privileged execution in KVM and Firecracker environments. This does not establish access to customer files or secrets. AlmaLinux confirmed impacts on versions 8, 9, and 10 and announced testing-repository patches on October 16. Operators must check host-kernel fixes and reboot requirements rather than only guest updates, without assuming every cloud is equally vulnerable.