{"id":"CVE-2025-40123","revision":"8e5d88b2358e4657bb3773f40ec4f5b4","records":[{"revision":"8e5d88b2358e4657bb3773f40ec4f5b4","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2025-40123","aliases":[],"title":"bpf: Enforce expected_attach_type for tailcall compatibility","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Enforce expected_attach_type for tailcall compatibility\n\nYinhao et al. recently reported:\n\n Our fuzzer tool discovered an uninitialized pointer issue in the\n bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem.\n This leads to a NULL pointer dereference when a BPF program attempts to\n deference the txq member of struct xdp_buff object.\n\nThe test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the\nentry point for bpf_prog_test_run_xdp() and its expected_attach_type can\nneither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot\nof a tailcall map it owns. progB's expected_attach_type must be BPF_XDP_DEVMAP\nto pass xdp_is_valid_access() validation. The program returns struct xdp_md's\negress_ifindex, and the latter is only allowed to be accessed under mentioned\nexpected_attach_type. progB is then inserted into the tailcall which progA\ncalls.\n\nThe underlying issue goes beyond XDP though. Another example are programs\nof type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well\nas sock_addr_func_proto() have different logic depending on the programs'\nexpected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME\nshould not be allowed doing a tailcall into a program which calls bpf_bind()\nout of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT.\n\nIn short, specifying expected_attach_type allows to open up additional\nfunctionality or restrictions beyond what the basic bpf_prog_type enables.\nThe use of tailcalls must not violate these constraints. Fix it by enforcing\nexpected_attach_type in __bpf_prog_map_compatible().\n\nNote that we only enforce this for tailcall maps, but not for BPF devmaps or\ncpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and\ncpu_map_bpf_prog_run*() which set up a new environment / context and therefore\nthese situations are not prone to this issue.","state":0,"publishedAt":"2025-11-12T10:23:19.589+00:00","modifiedAt":"2026-10-15T22:02:38.256+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/linux/bpf.h\",\n \"kernel/bpf/core.c\"\n ],\n \"versions\": [\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"e53a59e7cee5c1605d1ed595933098c2b69108f9\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"dc4f348952173beb8ceb15be30b249276eccb605\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"a99de19128aec0913f3d529f529fbbff5edfaff8\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"c1ad19b5d8e23123503dcaf2d4342e1b90b923ad\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5e43f899b03a3492ce5fc44e8900becb04dae9c0\",\n \"lessThan\": \"4540aed51b12bc13364149bf95f6ecef013197c0\",\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/linux/bpf.h\",\n \"kernel/bpf/core.c\"\n ],\n \"versions\": [\n {\n \"version\": \"4.17\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"4.17\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.270\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.221\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.156\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.112\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.53\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.17.3\",\n \"lessThanOrEqual\": \"6.17.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/e53a59e7cee5c1605d1ed595933098c2b69108f9","https://git.kernel.org/stable/c/dc4f348952173beb8ceb15be30b249276eccb605","https://git.kernel.org/stable/c/a99de19128aec0913f3d529f529fbbff5edfaff8","https://git.kernel.org/stable/c/08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32","https://git.kernel.org/stable/c/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a","https://git.kernel.org/stable/c/c1ad19b5d8e23123503dcaf2d4342e1b90b923ad","https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-40123","license":"CVE Program Terms of Use","key":"cve-program:CVE-2025-40123","identifiers":["CVE-2025-40123"]},"retained":false,"historicalAffected":[]}],"coverage":[]}