{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
          "defaultStatus": "unaffected",
          "packageName": "zephyr",
          "product": "zephyr",
          "programFiles": [
            "kernel/userspace/userspace.c"
          ],
          "vendor": "zephyrproject",
          "versions": [
            {
              "lessThan": "4.5.0",
              "status": "affected",
              "version": "2.0.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In Zephyr\u0027s 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\u0027s 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 \u0026=~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)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-362",
              "description": "race",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-25T13:23:07.028Z",
        "orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
        "shortName": "zephyr"
      },
      "references": [
        {
          "name": "Fix commit",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/zephyrproject-rtos/zephyr/commit/862ea2fbbeb2ccdf8ff994b03e2e3b4405f2c37d"
        },
        {
          "name": "GHSA-j693-5rh5-8g8h",
          "url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j693-5rh5-8g8h"
        }
      ],
      "title": "SMP race in `thread_idx_alloc()` lets concurrent `k_object_alloc(K_OBJ_THREAD)` callers share a kernel-object permission slot",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
    "assignerShortName": "zephyr",
    "cveId": "CVE-2026-10681",
    "datePublished": "2026-07-25T13:23:07.028Z",
    "dateReserved": "2026-06-02T15:26:11.951Z",
    "dateUpdated": "2026-07-25T13:23:07.028Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-10681",
      "date": "2026-07-26",
      "epss": "0.00079",
      "percentile": "0.00205"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-10681\",\"sourceIdentifier\":\"vulnerabilities@zephyrproject.org\",\"published\":\"2026-07-25T14:16:28.957\",\"lastModified\":\"2026-07-25T14:16:28.957\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In Zephyr\u0027s 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\u0027s 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 \u0026=~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).\"}],\"affected\":[{\"source\":\"vulnerabilities@zephyrproject.org\",\"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\":\"4.5.0\",\"versionType\":\"semver\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"vulnerabilities@zephyrproject.org\",\"type\":\"Secondary\",\"cvssData\":{\"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}]},\"weaknesses\":[{\"source\":\"vulnerabilities@zephyrproject.org\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-362\"}]}],\"references\":[{\"url\":\"https://github.com/zephyrproject-rtos/zephyr/commit/862ea2fbbeb2ccdf8ff994b03e2e3b4405f2c37d\",\"source\":\"vulnerabilities@zephyrproject.org\"},{\"url\":\"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j693-5rh5-8g8h\",\"source\":\"vulnerabilities@zephyrproject.org\"}]}}"
  }
}