{"id":"CVE-2026-64024","revision":"821b98d777064a3bba03274d84d89e92","records":[{"revision":"821b98d777064a3bba03274d84d89e92","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-64024","aliases":[],"title":"tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction","description":"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 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%","state":0,"publishedAt":"2026-07-19T15:39:16.598+00:00","modifiedAt":"2026-10-21T12:42:55.876+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"include/net/tcp.h\",\n                        \"net/ipv4/tcp.c\",\n                        \"net/ipv4/tcp_input.c\",\n                        \"net/ipv4/tcp_ipv4.c\",\n                        \"net/ipv6/tcp_ipv6.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"41eecbd712b73f0d5dcf1152b9a1c27b1f238028\",\n                            \"lessThan\": \"8bb6aa419b142dcc2680177ecc39c4c38db7fc16\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"41eecbd712b73f0d5dcf1152b9a1c27b1f238028\",\n                            \"lessThan\": \"e47f7060eaf60894e3e4d0e3c4fe6e1f2eacfbdd\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"41eecbd712b73f0d5dcf1152b9a1c27b1f238028\",\n                            \"lessThan\": \"4affe063fa56c880cbea8d0bfded0bb80751579d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"41eecbd712b73f0d5dcf1152b9a1c27b1f238028\",\n                            \"lessThan\": \"1bbf0ced1d9db73ac7893c2187f3459288603e0d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"include/net/tcp.h\",\n                        \"net/ipv4/tcp.c\",\n                        \"net/ipv4/tcp_input.c\",\n                        \"net/ipv4/tcp_ipv4.c\",\n                        \"net/ipv6/tcp_ipv6.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.10\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.10\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.114\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.34\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.0.11\",\n                            \"lessThanOrEqual\": \"7.0.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H","score":9.4,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/8bb6aa419b142dcc2680177ecc39c4c38db7fc16","https://git.kernel.org/stable/c/e47f7060eaf60894e3e4d0e3c4fe6e1f2eacfbdd","https://git.kernel.org/stable/c/4affe063fa56c880cbea8d0bfded0bb80751579d","https://git.kernel.org/stable/c/1bbf0ced1d9db73ac7893c2187f3459288603e0d"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64024","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-64024","identifiers":["CVE-2026-64024"]},"retained":false,"historicalAffected":[]}],"coverage":[]}