CVE-2026-10681

{
  "id": "CVE-2026-10681",
  "sourceIdentifier": "[email protected]",
  "published": "2026-07-25T14:16:28.957",
  "lastModified": "2026-10-24T13:10:00.147",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In Zephyr's userspace dynamic-objects subsystem, thread_idx_alloc() in kernel/userspace/userspace.c allocated a new thread permission index from the global _thread_idx_map[] bitmap without holding lists_lock.\n\nOn SMP systems, two user-mode threads invoking the k_object_alloc(K_OBJ_THREAD) syscall concurrently can both observe the same low free bit, perform the same non-atomic RMW to clear it, and return the identical tidx.\n\nThe two newly created K_OBJ_THREAD objects are then assigned the same thread_id, so the two user threads alias a single bit position in every kernel object's perms[] bitfield: any subsequent grant of access on a kernel object to one thread is implicitly a grant to the other, defeating userspace ACL isolation. A secondary lost-update window between the unlocked &=~BIT() in alloc and the locked |= BIT() in thread_idx_free() can also leak entries from the thread-index pool.\n\nThe defect is reachable from any user-mode thread via the unrestricted __syscall k_object_alloc and is gated on CONFIG_USERSPACE, CONFIG_DYNAMIC_OBJECTS, and CONFIG_SMP. The flaw was introduced when the per-thread permission index was added in 2018 and is present in every release up to and including v4.4.0. Fixed by holding lists_lock across the bitmap RMW and the permissions clear (and inlining the obj_list traversal that previously took the lock itself)."
    },
    {
      "lang": "es",
      "value": "En el subsistema de objetos dinámicos del espacio de usuario de Zephyr, thread_idx_alloc() en kernel/userspace/userspace.c asignó un nuevo índice de permiso de hilo del mapa de bits global _thread_idx_map[] sin mantener lists_lock.\n\nEn sistemas SMP, dos hilos en modo usuario que invocan la llamada al sistema k_object_alloc(K_OBJ_THREAD) concurrentemente pueden observar el mismo bit libre más bajo, realizar la misma operación RMW no atómica para borrarlo y devolver el tidx idéntico.\n\nA los dos objetos K_OBJ_THREAD recién creados se les asigna entonces el mismo thread_id, por lo que los dos hilos de usuario hacen alias a una única posición de bit en el campo de bits perms[] de cada objeto del kernel: cualquier concesión posterior de acceso en un objeto del kernel a un hilo es implícitamente una concesión al otro, lo que anula el aislamiento de ACL del espacio de usuario. Una ventana secundaria de actualización perdida entre el &=~BIT() desbloqueado en alloc y el |= BIT() bloqueado en thread_idx_free() también puede filtrar entradas del grupo de índices de hilos.\n\nEl defecto es alcanzable desde cualquier hilo en modo usuario a través de la llamada al sistema __syscall k_object_alloc sin restricciones y está condicionado por CONFIG_USERSPACE, CONFIG_DYNAMIC_OBJECTS y CONFIG_SMP. La falla fue introducida cuando se añadió el índice de permiso por hilo en 2018 y está presente en cada versión hasta la v4.4.0 inclusive. Solucionado manteniendo lists_lock durante la operación RMW del mapa de bits y la limpieza de permisos (e inlining la traversión de obj_list que previamente tomaba el bloqueo por sí misma)."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "zephyrproject",
          "product": "zephyr",
          "defaultStatus": "unaffected",
          "collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
          "packageName": "zephyr",
          "programFiles": [
            "kernel/userspace/userspace.c"
          ],
          "versions": [
            {
              "version": "2.0.0",
              "lessThan": "4.4.2",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
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        "source": "[email protected]",
        "type": "Secondary",
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          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "attackVector": "LOCAL",
          "attackComplexity": "HIGH",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 1.0,
        "impactScore": 5.5
      },
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        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
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          "baseScore": 7.0,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "HIGH",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.0,
        "impactScore": 5.9
      }
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    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-27T14:34:32.663266Z",
          "id": "CVE-2026-10681",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
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            {
              "technicalImpact": "total"
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          "role": "CISA Coordinator",
          "version": "2.0.3"
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  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-362"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
              "criteria": "cpe:2.3:o:zephyrproject:zephyr:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "2.0.0",
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  "references": [
    {
      "url": "https://github.com/zephyrproject-rtos/zephyr/commit/862ea2fbbeb2ccdf8ff994b03e2e3b4405f2c37d",
      "source": "[email protected]",
      "tags": [
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    {
      "url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j693-5rh5-8g8h",
      "source": "[email protected]",
      "tags": [
        "Exploit",
        "Patch",
        "Vendor Advisory"
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    }
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}