Linux's stable kernels shipped a fix on October 11 and 15, 2026 for CVE-2026-98432, a use-after-free in the IPv4 TCP handshake that a remote, unauthenticated peer can reach. The kernel's own CVE Numbering Authority (CNA) scores it CVSS 3.1 9.8, Critical. The fixed releases are 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10, and 7.3, and the bug goes back to Linux 4.4. The upstream fix is a four-line change, but most servers run a distribution's kernel, and as of 8:00 PM CDT, October 29, Ubuntu's tracker still reads "Vulnerable" for its kernel on every release, and Red Hat lists RHEL 8, 9, and 10 as affected with no fix.
Linux from 4.4 on, below 5.10.272 / 5.15.223 / 6.1.190 / 6.6.159 / 6.12.113 / 6.18.56 / 7.2.10. Distribution kernels follow their own versions: check the tracker.
