{"id":"CVE-2026-64024","title":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction\n\nBlamed commit moved the TIME_WAIT-derived ISN from the skb control\nblock to a per-CPU variable, assuming…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction\n\nBlamed commit moved the TIME_WAIT-derived ISN from the skb control\nblock to a per-CPU variable, assuming…","severity":"critical","cvss":9.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H","cwe":["CWE-401"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 6.10, < 6.18.34","linux_kernel >= 6.19, < 7.0.11","linux_kernel = 7.1"],"patched":["linux_kernel 7.0.11"],"published":"2026-07-19","updated":"2026-10-13","sourceUpdated":"2026-10-13T15:00:30.167","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64024","references":[{"url":"https://git.kernel.org/stable/c/1bbf0ced1d9db73ac7893c2187f3459288603e0d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4affe063fa56c880cbea8d0bfded0bb80751579d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e47f7060eaf60894e3e4d0e3c4fe6e1f2eacfbdd","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00385,"epssPercentile":0.30735,"ingestedAt":"2026-10-13T15:33:40.025Z","slug":"CVE-2026-64024","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction\n\nBlamed commit moved the TIME_WAIT-derived ISN from the skb control\nblock to a per-CPU variable, assuming the value would always be consumed\nby tcp_conn_request() for the same packet that wrote it. That assumption\nis violated by multiple drop paths between the producer\n(__this_cpu_write(tcp_tw_isn, isn) in tcp_v{4,6}_rcv()) and the consumer\n(tcp_conn_request()):\n\n - min_ttl / min_hopcount check\n - xfrm policy check\n - tcp_inbound_hash() MD5/AO mismatch\n - tcp_filter() eBPF/SO_ATTACH_FILTER drop\n - th->syn && th->fin discard in tcp_rcv_state_process() TCP_LISTEN\n - psp_sk_rx_policy_check() in tcp_v{4,6}_do_rcv()\n - tcp_checksum_complete() in tcp_v{4,6}_do_rcv()\n - tcp_v{4,6}_cookie_check() returning NULL\n\nWhen a packet is dropped on any of these paths, tcp_tw_isn is left set.\n\nThe next SYN processed on the same CPU then consumes the non zero value in\ntcp_conn_request(), receiving a potentially predictable ISN.\n\nThis patch moves back tcp_tw_isn to skb->cb[], getting rid of the per-cpu\nvariable.\n\nNote that tcp_v{4,6}_fill_cb() do not set it.\n\nVery litle impact on overall code size/complexity:\n\n$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new\nadd/remove: 0/0 grow/shrink: 2/1 up/down: 8/-15 (-7)\nFunction                                     old     new   delta\ntcp_v6_rcv                                  3038    3042      +4\ntcp_v4_rcv                                  3035    3039      +4\ntcp_conn_request                            2938    2923     -15\nTotal: Before=24436060, After=24436053, chg -0.00%\n\n## Affected\n\n- `linux_kernel >= 6.10, < 6.18.34`\n- `linux_kernel >= 6.19, < 7.0.11`\n- `linux_kernel = 7.1`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 7.0.11`","depth":"midnight","depthScore":52,"depthScoreParts":{"impact":51.7,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}