{"id":"CVE-2026-80585","revision":"a15f0a580a37431bad6cb586ef3ee73a","records":[{"revision":"a15f0a580a37431bad6cb586ef3ee73a","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-80585","aliases":[],"title":"mptcp: fastopen: only mark MPTFO subflows with SYN data","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fastopen: only mark MPTFO subflows with SYN data\n\nPassive TCP Fast Open accepts a valid-cookie SYN even when it carries\nno data. In that case the child socket's receive queue is intentionally\nleft empty.\n\nmptcp_fastopen_subflow_synack_set_params() set is_mptfo before checking\nfor queued SYN data. That made data-less TFO SYNs hit a WARN and, if\nthe warning was non-fatal, left stale MPTFO state behind. The stale\nflag could later trigger a state-confusion bug in\ncheck_fully_established().\n\nOnly mark the subflow as MPTFO after confirming that an SKB was queued.\nReturn quietly when the receive queue is empty.\n\nNote that mptcp_subflow_context's is_mptfo field is now not just about\nsubflows where the TFO was present, but about MPTFO subflow that\nconsumed SYN data. Only having a valid cookie but not carrying data is\nnot really \"doing TFO\".","state":0,"publishedAt":"2026-08-26T14:37:40.901+00:00","modifiedAt":"2026-10-16T19:26:28.485+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                        \"net/mptcp/fastopen.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"36b122baf6a8bd46b4a591f12f4ed17b22257408\",\n                            \"lessThan\": \"f75f174edc865738522e514d042cf5627f084859\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"36b122baf6a8bd46b4a591f12f4ed17b22257408\",\n                            \"lessThan\": \"fca7e444c04689fe4cc6b56f2725f804a4bb1ef9\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"36b122baf6a8bd46b4a591f12f4ed17b22257408\",\n                            \"lessThan\": \"75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"36b122baf6a8bd46b4a591f12f4ed17b22257408\",\n                            \"lessThan\": \"72b4a0c51a4b550d40301d60a366b429b8c8e78d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"36b122baf6a8bd46b4a591f12f4ed17b22257408\",\n                            \"lessThan\": \"e00b63056fb4f261455b3e5df5268a1f8ce47a87\",\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                        \"net/mptcp/fastopen.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.2\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.2\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.153\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.105\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.46\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1.10\",\n                            \"lessThanOrEqual\": \"7.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2\",\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/f75f174edc865738522e514d042cf5627f084859","https://git.kernel.org/stable/c/fca7e444c04689fe4cc6b56f2725f804a4bb1ef9","https://git.kernel.org/stable/c/75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5","https://git.kernel.org/stable/c/72b4a0c51a4b550d40301d60a366b429b8c8e78d","https://git.kernel.org/stable/c/e00b63056fb4f261455b3e5df5268a1f8ce47a87"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-80585","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-80585","identifiers":["CVE-2026-80585"]},"retained":false,"historicalAffected":[]}],"coverage":[]}