{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "io_uring/memmap.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "c6a2706e08b8a1b2d3740161c0977d38e596c1ee",
              "status": "affected",
              "version": "087f997870a948820ec366701d178f402c6a23a3",
              "versionType": "git"
            },
            {
              "lessThan": "a69a9b53c54e2d33e2a5b1ea4a9a71fd01c6cf3a",
              "status": "affected",
              "version": "087f997870a948820ec366701d178f402c6a23a3",
              "versionType": "git"
            },
            {
              "lessThan": "33503c083fda048c77903460ac0429e1e2c0e341",
              "status": "affected",
              "version": "087f997870a948820ec366701d178f402c6a23a3",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "io_uring/memmap.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.14"
            },
            {
              "lessThan": "6.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.15.*",
              "status": "unaffected",
              "version": "6.15.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.16.*",
              "status": "unaffected",
              "version": "6.16.2",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.15.11",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.16.2",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/memmap: cast nr_pages to size_t before shifting\n\nIf the allocated size exceeds UINT_MAX, then it\u0027s necessary to cast\nthe mr-\u003enr_pages value to size_t to prevent it from overflowing. In\npractice this isn\u0027t much of a concern as the required memory size will\nhave been validated upfront, and accounted to the user. And \u003e 4GB sizes\nwill be necessary to make the lack of a cast a problem, which greatly\nexceeds normal user locked_vm settings that are generally in the kb to\nmb range. However, if root is used, then accounting isn\u0027t done, and\nthen it\u0027s possible to hit this issue."
        }
      ],
      "metrics": [
        {
          "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 bug is reached purely through local syscalls \u2014 `io_uring_setup()` followed by `io_uring_register(IORING_REGISTER_MEM_REGION)` with an attacker-chosen `io_uring_region_desc.size`. Per kernel guidance, io_uring is a local attack vector.\nAC:L - This is a deterministic integer truncation fully controlled by the attacker\u0027s chosen region size (any value \u2265 4 GB with a small remainder); there is no race, no memory-layout dependency, and no condition outside the attacker\u0027s control. The only environmental factor is RLIMIT_MEMLOCK/CAP_IPC_LOCK, which is a target configuration rather than a probabilistic exploitation condition.\nPR:L - `io_uring_setup` and `IORING_REGISTER_MEM_REGION` require no capability at all under the default `kernel.io_uring_disabled=0`; the only gate is the `RLIMIT_MEMLOCK` counter check, which no actual memory allocation must satisfy since the allocation itself is truncated. On the many real deployments where non-root users have memlock unlimited (container runtimes, RDMA/OFED and DPDK hosts, HPC nodes, database service accounts), an ordinary unprivileged local user reaches this directly; with real root (`CAP_IPC_LOCK` in init_user_ns) accounting is skipped entirely.\nUI:N - The attacker performs the entire sequence \u2014 ring setup, region registration, and mmap of the param region \u2014 within their own process. No victim action is involved.\nS:U - The corruption and its consequences are contained within the kernel\u0027s own security authority on the same host; no VM, IOMMU, or hypervisor boundary is crossed.\nC:H - The truncation causes `mr-\u003epages[]` to be populated with `struct page` pointers spanning ~4 GB of unrelated physical memory, which is then `vmap()`ed into the kernel and mmap-able into userspace via `io_region_mmap()`/`vm_insert_pages()`. This yields direct read access to arbitrary physical memory belonging to other processes and the kernel.\nI:H - The same foreign pages are inserted into a writable user VMA and aliased writable in the kernel vmap, giving an arbitrary physical-memory write primitive (e.g. modifying cached setuid binary text or kernel data), and `insert_page_into_pte_locked()` performs `folio_get()`/rmap accounting on folios the region never owned, corrupting refcounts into a use-after-free. This is straightforwardly leveraged into privilege escalation.\nA:H - `io_check_coalesce_buffer()` dereferences ~1M out-of-range `struct page` pointers, oopsing whenever the walk crosses unpopulated vmemmap, and the resulting refcount corruption/UAF on in-use pages causes kernel panics. Any local user able to trigger it can crash the machine repeatedly."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:05:14.029Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/c6a2706e08b8a1b2d3740161c0977d38e596c1ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/a69a9b53c54e2d33e2a5b1ea4a9a71fd01c6cf3a"
        },
        {
          "url": "https://git.kernel.org/stable/c/33503c083fda048c77903460ac0429e1e2c0e341"
        }
      ],
      "title": "io_uring/memmap: cast nr_pages to size_t before shifting",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39793",
    "datePublished": "2025-09-12T15:59:30.388Z",
    "dateReserved": "2025-04-16T07:20:57.132Z",
    "dateUpdated": "2026-08-05T12:05:14.029Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}