CVE-2025-40123 (GCVE-0-2025-40123)

Vulnerability from cvelistv5 – Published: 2025-11-12 10:23 – Updated: 2026-10-15 22:02
VLAI
Title
bpf: Enforce expected_attach_type for tailcall compatibility
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Enforce expected_attach_type for tailcall compatibility Yinhao et al. recently reported: Our fuzzer tool discovered an uninitialized pointer issue in the bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem. This leads to a NULL pointer dereference when a BPF program attempts to deference the txq member of struct xdp_buff object. The test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the entry point for bpf_prog_test_run_xdp() and its expected_attach_type can neither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot of a tailcall map it owns. progB's expected_attach_type must be BPF_XDP_DEVMAP to pass xdp_is_valid_access() validation. The program returns struct xdp_md's egress_ifindex, and the latter is only allowed to be accessed under mentioned expected_attach_type. progB is then inserted into the tailcall which progA calls. The underlying issue goes beyond XDP though. Another example are programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well as sock_addr_func_proto() have different logic depending on the programs' expected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME should not be allowed doing a tailcall into a program which calls bpf_bind() out of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT. In short, specifying expected_attach_type allows to open up additional functionality or restrictions beyond what the basic bpf_prog_type enables. The use of tailcalls must not violate these constraints. Fix it by enforcing expected_attach_type in __bpf_prog_map_compatible(). Note that we only enforce this for tailcall maps, but not for BPF devmaps or cpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and cpu_map_bpf_prog_run*() which set up a new environment / context and therefore these situations are not prone to this issue.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-15 21:57 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < e53a59e7cee5c1605d1ed595933098c2b69108f9 (git)
Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < dc4f348952173beb8ceb15be30b249276eccb605 (git)
Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < a99de19128aec0913f3d529f529fbbff5edfaff8 (git)
Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < 08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32 (git)
Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a (git)
Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < c1ad19b5d8e23123503dcaf2d4342e1b90b923ad (git)
Affected: 5e43f899b03a3492ce5fc44e8900becb04dae9c0 , < 4540aed51b12bc13364149bf95f6ecef013197c0 (git)
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Linux Linux Affected: 4.17
Unaffected: 0 , < 4.17 (semver)
Unaffected: 5.10.270 , ≤ 5.10.* (semver)
Unaffected: 5.15.221 , ≤ 5.15.* (semver)
Unaffected: 6.1.156 , ≤ 6.1.* (semver)
Unaffected: 6.6.112 , ≤ 6.6.* (semver)
Unaffected: 6.12.53 , ≤ 6.12.* (semver)
Unaffected: 6.17.3 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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Show details on NVD website
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          "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\u0027s 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\u0027s expected_attach_type must be BPF_XDP_DEVMAP\nto pass xdp_is_valid_access() validation. The program returns struct xdp_md\u0027s\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\u0027\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."
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              "value": "AV:L - The vulnerability is reached through the bpf(2) syscall \u2014 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 \u2014 program load, map update, and program invocation \u2014 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-\u003etxq, 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 \u2014 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 \u2014 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-\u003etxq in bpf_prog_test_run_xdp(), and in driver XDP paths the uninitialized txq produces a wild pointer dereference \u2014 either way a kernel oops that the attacker can trigger repeatedly."
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            "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\u0027s 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\u0027s expected_attach_type must be BPF_XDP_DEVMAP\nto pass xdp_is_valid_access() validation. The program returns struct xdp_md\u0027s\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\u0027\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."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbpf: Hacer cumplir expected_attach_type para la compatibilidad de tailcall\n\nYinhao et al. informaron recientemente:\n\n  Nuestra herramienta de fuzzing descubri\u00f3 un problema de puntero no\n  inicializado en la funci\u00f3n bpf_prog_test_run_xdp() dentro del subsistema\n  BPF del kernel de Linux. Esto lleva a una desreferencia de puntero NULL\n  cuando un programa BPF intenta desreferenciar el miembro txq del objeto\n  struct xdp_buff.\n\nLa prueba inicializa dos programas de BPF_PROG_TYPE_XDP: progA act\u00faa como\npunto de entrada para bpf_prog_test_run_xdp() y su expected_attach_type no\npuede ser ni BPF_XDP_DEVMAP ni BPF_XDP_CPUMAP. progA llama a una ranura de\nun mapa de tailcall que posee. El expected_attach_type de progB debe ser\nBPF_XDP_DEVMAP para pasar la validaci\u00f3n de xdp_is_valid_access(). El\nprograma devuelve el egress_ifindex de struct xdp_md, y este \u00faltimo solo\npuede ser accedido bajo el expected_attach_type mencionado. progB se inserta\nentonces en el tailcall al que llama progA.\n\nSin embargo, el problema subyacente va m\u00e1s all\u00e1 de XDP. Otro ejemplo son los\nprogramas de tipo BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access()\nas\u00ed como sock_addr_func_proto() tienen l\u00f3gica diferente dependiendo del\nexpected_attach_type de los programas. De manera similar, un programa\nadjunto a BPF_CGROUP_INET4_GETPEERNAME no deber\u00eda permit\u00edrsele hacer un\ntailcall a un programa que llama a bpf_bind() fuera de BPF, lo cual solo\nest\u00e1 habilitado para BPF_CGROUP_INET4_CONNECT.\n\nEn resumen, especificar expected_attach_type permite habilitar funcionalidad\no restricciones adicionales m\u00e1s all\u00e1 de lo que permite el bpf_prog_type\nb\u00e1sico. El uso de tailcalls no debe violar estas restricciones. Se soluciona\nhaciendo cumplir expected_attach_type en __bpf_prog_map_compatible().\n\nTenga en cuenta que solo hacemos cumplir esto para los mapas de tailcall,\npero no para los devmaps o cpumaps de BPF: All\u00ed, los programas se invocan a\ntrav\u00e9s de dev_map_bpf_prog_run*() y cpu_map_bpf_prog_run*() que configuran\nun nuevo entorno/contexto y, por lo tanto, estas situaciones no son\npropensas a este problema."
          }
        ],
        "id": "CVE-2025-40123",
        "lastModified": "2026-10-19T21:10:00.160",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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                "options": [
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                  {
                    "technicalImpact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-15T21:57:04.979824Z",
                "version": "2.0.3"
              }
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          ]
        },
        "published": "2025-11-12T11:15:41.807",
        "references": [
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          },
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            "url": "https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0"
          },
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          },
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/dc4f348952173beb8ceb15be30b249276eccb605"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/e53a59e7cee5c1605d1ed595933098c2b69108f9"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-07-30T10:08:14+00:00",
      "cve": "CVE-2025-40123",
      "id": "CVE-2025-40123",
      "initial_release_date": "2025-11-12T00:00:00+00:00",
      "product_status:known_affected": "260",
      "product_status:known_not_affected": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Enforce expected_attach_type for tailcall compatibility",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40123.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2025-40123",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-10-15T21:57:04.979824Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-10-15T21:57:05.943Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "include/linux/bpf.h",
                "kernel/bpf/core.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "e53a59e7cee5c1605d1ed595933098c2b69108f9",
                  "status": "affected",
                  "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0",
                  "versionType": "git"
                },
                {
                  "lessThan": "dc4f348952173beb8ceb15be30b249276eccb605",
                  "status": "affected",
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                  "status": "affected",
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                  "status": "affected",
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                  "versionType": "git"
                },
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                  "status": "affected",
                  "version": "5e43f899b03a3492ce5fc44e8900becb04dae9c0",
                  "versionType": "git"
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            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "include/linux/bpf.h",
                "kernel/bpf/core.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "4.17"
                },
                {
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                  "version": "0",
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                  "version": "6.1.156",
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                  "lessThanOrEqual": "6.6.*",
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                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.53",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.17.*",
                  "status": "unaffected",
                  "version": "6.17.3",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.18",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
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              "nodes": [
                {
                  "cpeMatch": [
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                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.10.270",
                      "versionStartIncluding": "4.17",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                    {
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                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "negate": false,
                  "operator": "OR"
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          "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\u0027s 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\u0027s expected_attach_type must be BPF_XDP_DEVMAP\nto pass xdp_is_valid_access() validation. The program returns struct xdp_md\u0027s\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\u0027\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": [
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              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The vulnerability is reached through the bpf(2) syscall \u2014 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 \u2014 program load, map update, and program invocation \u2014 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-\u003etxq, 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 \u2014 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 \u2014 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-\u003etxq in bpf_prog_test_run_xdp(), and in driver XDP paths the uninitialized txq produces a wild pointer dereference \u2014 either way a kernel oops that the attacker can trigger repeatedly."
                }
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            "dateUpdated": "2026-09-14T11:58:08.635Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
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            },
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              "url": "https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0"
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          "title": "bpf: Enforce expected_attach_type for tailcall compatibility",
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        "cveId": "CVE-2025-40123",
        "datePublished": "2025-11-12T10:23:19.589Z",
        "dateReserved": "2025-04-16T07:20:57.169Z",
        "dateUpdated": "2026-10-15T22:02:38.256Z",
        "state": "PUBLISHED"
      },
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  }
}



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