Linux kernel TCP vulnerability receives a CVSS score of 9.8, affecting distributions including Ubuntu and Red Hat

The race condition vulnerability CVE-2026-98432 in the Linux kernel TCP code affects distributions including Ubuntu and RHEL, was rated 9.8 by the kernel CVE team, and as of October 29 Ubuntu and RHEL had not yet released fixed kernels. Anthropic said its model Claude autonomously wrote a two-stage exploit chain: first leaking kernel addresses in about 48 minutes to bypass KASLR, then overwriting a callback pointer via a buffer overflow, and about 5 minutes later executing commands as root, targeting servers with multipath TCP enabled. The vulnerability is a use-after-free when IPv4 TCP establishes a connection, was introduced in Linux 4.4, and was fixed upstream on October 5 with thanks to Anthropic researcher Xinyang Ge.