{"id":"CVE-2021-47593","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: clear 'kern' flag from fallback sockets\n\nThe mptcp ULP extension relies on sk-\u003esk_sock_kern being set correctly:\nIt prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, \"mptcp\", 6); from\nworking for plain tcp sockets (any userspace-exposed socket).\n\nBut in case of fallback, accept() can return a plain tcp sk.\nIn such case, sk is still tagged as 'kernel' and setsockopt will work.\n\nThis will crash the kernel, The subflow extension has a NULL ctx-\u003econn\nmptcp socket:\n\nBUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0\nCall Trace:\n tcp_data_ready+0xf8/0x370\n [..]","modified":"2026-03-13T05:20:49.659034Z","published":"2024-06-19T15:15:53.890Z","related":["SUSE-SU-2024:2894-1","SUSE-SU-2024:2939-1","SUSE-SU-2024:2947-1"],"references":[{"type":"FIX","url":"https://git.kernel.org/stable/c/c26ac0ea3a91c210cf90452e625dc441adf3e549"},{"type":"FIX","url":"https://git.kernel.org/stable/c/d6692b3b97bdc165d150f4c1505751a323a80717"},{"type":"FIX","url":"https://git.kernel.org/stable/c/451f1eded7f56e93aaf52eb547ba97742d9c0e97"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2021-47593.json","unresolved_ranges":[{"events":[{"introduced":"5.6"},{"fixed":"5.10.88"}]},{"events":[{"introduced":"5.11"},{"fixed":"5.15.11"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc1"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc2"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc3"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc4"}]},{"events":[{"introduced":"0"},{"last_affected":"5.16-rc5"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}