{"id":"CVE-2025-68227","summary":"mptcp: Fix proto fallback detection with BPF","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: Fix proto fallback detection with BPF\n\nThe sockmap feature allows bpf syscall from userspace, or based\non bpf sockops, replacing the sk_prot of sockets during protocol stack\nprocessing with sockmap's custom read/write interfaces.\n'''\ntcp_rcv_state_process()\n  syn_recv_sock()/subflow_syn_recv_sock()\n    tcp_init_transfer(BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB)\n      bpf_skops_established       \u003c== sockops\n        bpf_sock_map_update(sk)   \u003c== call bpf helper\n          tcp_bpf_update_proto()  \u003c== update sk_prot\n'''\n\nWhen the server has MPTCP enabled but the client sends a TCP SYN\nwithout MPTCP, subflow_syn_recv_sock() performs a fallback on the\nsubflow, replacing the subflow sk's sk_prot with the native sk_prot.\n'''\nsubflow_syn_recv_sock()\n  subflow_ulp_fallback()\n    subflow_drop_ctx()\n      mptcp_subflow_ops_undo_override()\n'''\n\nThen, this subflow can be normally used by sockmap, which replaces the\nnative sk_prot with sockmap's custom sk_prot. The issue occurs when the\nuser executes accept::mptcp_stream_accept::mptcp_fallback_tcp_ops().\nHere, it uses sk-\u003esk_prot to compare with the native sk_prot, but this\nis incorrect when sockmap is used, as we may incorrectly set\nsk-\u003esk_socket-\u003eops.\n\nThis fix uses the more generic sk_family for the comparison instead.\n\nAdditionally, this also prevents a WARNING from occurring:\n\nresult from ./scripts/decode_stacktrace.sh:\n------------[ cut here ]------------\nWARNING: CPU: 0 PID: 337 at net/mptcp/protocol.c:68 mptcp_stream_accept \\\n(net/mptcp/protocol.c:4005)\nModules linked in:\n...\n\nPKRU: 55555554\nCall Trace:\n\u003cTASK\u003e\ndo_accept (net/socket.c:1989)\n__sys_accept4 (net/socket.c:2028 net/socket.c:2057)\n__x64_sys_accept (net/socket.c:2067)\nx64_sys_call (arch/x86/entry/syscall_64.c:41)\ndo_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)\nentry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\nRIP: 0033:0x7f87ac92b83d\n\n---[ end trace 0000000000000000 ]---","modified":"2026-04-16T04:31:51.321221929Z","published":"2025-12-16T13:57:20.027Z","related":["SUSE-SU-2026:0447-1","SUSE-SU-2026:0472-1","SUSE-SU-2026:0587-1","SUSE-SU-2026:20477-1","SUSE-SU-2026:20498-1","SUSE-SU-2026:20555-1","SUSE-SU-2026:20599-1","SUSE-SU-2026:20615-1","SUSE-SU-2026:20845-1","SUSE-SU-2026:20876-1","openSUSE-SU-2026:20287-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68227.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/037cc50589643342d69185b663ecf9d26cce91e8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1a0d5c74af9b6ba9ffdf1172de5a1a6df5922a00"},{"type":"WEB","url":"https://git.kernel.org/stable/c/344974ea1a3ca30e4920687b0091bda4438cebdb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7ee8f015eb47907745e2070184a8ab1e442ac3c4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/92c4092fe012ecdfa5fb05d394f1c1d8f91ad81c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9b1980b6f23fa30bf12add19f37c7458625099eb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c77b3b79a92e3345aa1ee296180d1af4e7031f8f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68227.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-68227"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0b4f33def7bbde1ce2fea05f116639270e7acdc7"},{"fixed":"92c4092fe012ecdfa5fb05d394f1c1d8f91ad81c"},{"fixed":"7ee8f015eb47907745e2070184a8ab1e442ac3c4"},{"fixed":"344974ea1a3ca30e4920687b0091bda4438cebdb"},{"fixed":"037cc50589643342d69185b663ecf9d26cce91e8"},{"fixed":"9b1980b6f23fa30bf12add19f37c7458625099eb"},{"fixed":"1a0d5c74af9b6ba9ffdf1172de5a1a6df5922a00"},{"fixed":"c77b3b79a92e3345aa1ee296180d1af4e7031f8f"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-68227.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.7.0"},{"fixed":"5.10.247"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.197"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.159"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.118"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.60"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.17.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-68227.json"}}],"schema_version":"1.7.5"}