{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-40123", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.169Z", "datePublished": "2025-11-12T10:23:19.589Z", "dateUpdated": "2026-08-05T12:07:56.107Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:07:56.107Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerability is reached through the bpf(2) syscall — loading two programs with differing expected_attach_type, populating a BPF_MAP_TYPE_PROG_ARRAY, and invoking the tail call via BPF_PROG_TEST_RUN or a live attach. No network-supplied data introduces the incompatible tail call, so local access is required.\nAC:L - Exploitation is fully deterministic: the attacker authors and loads both programs, owns the prog array, and controls exactly when the tail call executes; there is no race and no memory-layout condition needed for the mis-typed context dereference to occur.\nPR:L - A basic local user with BPF program-loading access can create the prog array and the two mismatched programs; this matches the established scoring of comparable BPF verifier-constraint bypasses, and containerized/delegated-token deployments grant exactly this level without full administrative rights.\nUI:N - The attacker performs every step — program load, map update, and program invocation — entirely on their own; no victim action or cooperation is involved.\nS:U - The mis-typed context dereference and any resulting corruption occur within the kernel that is already the vulnerable component, so impact stays inside a single security authority.\nC:H - xdp_init_buff() never initializes xdp_buff->txq, so a tail-called BPF_XDP_DEVMAP program reading egress_ifindex dereferences attacker-groomable uninitialized stack memory twice and returns the resulting kernel dword into BPF, which can be exfiltrated through a map — an effectively arbitrary kernel read primitive.\nI:H - Bypassing expected_attach_type lets a program execute helpers and context writes the running hook never validated — e.g. bpf_bind()/__inet_bind() invoked from a GETPEERNAME hook mutates live socket binding and hash state without the socket lock, and msg_src_ip4/6 or sockopt level/optname/retval writes land on NULL or wrong-type kernel fields.\nA:H - The reported case is an immediate NULL pointer dereference on xdp_buff->txq in bpf_prog_test_run_xdp(), and in driver XDP paths the uninitialized txq produces a wild pointer dereference — either way a kernel oops that the attacker can trigger repeatedly." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/bpf.h", "kernel/bpf/core.c" ], "versions": [ { "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0", "lessThan": "a99de19128aec0913f3d529f529fbbff5edfaff8", "status": "affected", "versionType": "git" }, { "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0", "lessThan": "08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32", "status": "affected", "versionType": "git" }, { "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0", "lessThan": "f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a", "status": "affected", "versionType": "git" }, { "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0", "lessThan": "c1ad19b5d8e23123503dcaf2d4342e1b90b923ad", "status": "affected", "versionType": "git" }, { "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0", "lessThan": "4540aed51b12bc13364149bf95f6ecef013197c0", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/bpf.h", "kernel/bpf/core.c" ], "versions": [ { "version": "4.17", "status": "affected" }, { "version": "0", "lessThan": "4.17", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.156", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.112", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.53", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.17.3", "lessThanOrEqual": "6.17.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.1.156" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.6.112" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.12.53" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.17.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.18" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a99de19128aec0913f3d529f529fbbff5edfaff8" }, { "url": "https://git.kernel.org/stable/c/08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32" }, { "url": "https://git.kernel.org/stable/c/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a" }, { "url": "https://git.kernel.org/stable/c/c1ad19b5d8e23123503dcaf2d4342e1b90b923ad" }, { "url": "https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0" } ], "title": "bpf: Enforce expected_attach_type for tailcall compatibility", "x_generator": { "engine": "bippy-1.2.0" } } } }