Linux kernel critical vulnerability PwnEscape allows virtual machines to read host memory

Security company pwn.ai researcher Paulos Yibelo disclosed a critical vulnerability CVE-2026-99999 (codename PwnEscape) in Linux kernel networking code that can read host memory from a virtual machine. The issue was demonstrated on Vercel's production sandbox and confirmed by Vercel. Each packet can retrieve about 32 bytes of host memory, and two specially crafted packets can crash the host and bring down all sandboxes on it; the crash and code execution were only reproduced on a machine built by the researcher according to Vercel's configuration, and the researcher stated this is not a claim of root command execution on any vendor's production environment. The fix is kernel commit 6785011f8b16, which the author describes as a defense-in-depth measure, backported to stable branches such as 5.10.272, 6.6.159, and 6.12.113. The CVE record is rated 9.3 (Critical), with an attack vector of local, requiring the attacker to already run code inside the guest, and no actual attacks have been reported.