pwn.ai discloses PwnEscape details: GPT-5.6 Sol helped discover a Linux networking stack flaw enabling KVM guest-to-host escape (CVE-2026-99999)

pwn.ai discloses technical details of CVE-2026-99999: a delayed write in Linux kernel IPv4 checksum handling can rewrite an already-checksummed IPv4 header, and researchers used this in their own KVM environment to achieve guest-to-host escape. The root cause is that checksum metadata is not compared against network header boundaries before completion; it initially manifested as a 32-byte host memory leak per occurrence, then a 64-byte kernel write was demonstrated in their own test environment, and after four cold boots a host root helper program was executed. The research was completed during the $1 million Sandbox challenge launched by Vercel on August 18, 2026, using pwn.ai's Omega-Pwn research framework with GPT-5.6 Sol as the primary reasoning engine. The upstream fix 6785011f8b16 adds ip_check_csum_start checks to five IPv4 checksum completion paths and entered net.git on October 8.