Linux Kernel TCP Flaw With 9.8 CVSS Score Affects Ubuntu, Red Hat and Other Distributions

A race-condition use-after-free in the Linux kernel's IPv4 TCP connection setup, identified as CVE-2026-98432, has been scored 9.8/10 by the kernel's own CVE team, though Red Hat, Amazon, Oracle and SUSE rate it lower (5.9–8.1). The bug, present since Linux 4.4 and fixed upstream on October 5, lets attackers trigger use of already-freed memory tied to IP options during the TCP handshake, potentially leaking kernel memory, corrupting it, or crashing the system. Anthropic disclosed on October 27 that its Claude AI model independently wrote a working two-stage exploit—bypassing KASLR and then hijacking a callback pointer—to gain remote root code execution on servers running a multipath TCP (MPTCP) listener, with no reported attacks in the wild as of October 29. While Debian, Oracle Linux, SUSE and some Amazon Linux builds have already shipped patched kernels, Ubuntu and Red Hat Enterprise Linux have not yet released fixes, leaving many production systems exposed; admins should update where patched kernels (e.g., Linux 6.12.113, 6.18.56) are available and monitor vendor advisories closely.