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CVE-2025-71070 (GCVE-0-2025-71070)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:31 – Updated: 2026-08-05 12:11
VLAI
Title
ublk: clean up user copy references on ublk server exit
Summary
In the Linux kernel, the following vulnerability has been resolved: ublk: clean up user copy references on ublk server exit If a ublk server process releases a ublk char device file, any requests dispatched to the ublk server but not yet completed will retain a ref value of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 ("ublk: simplify aborting ublk request"), __ublk_fail_req() would decrement the reference count before completing the failed request. However, that commit optimized __ublk_fail_req() to call __ublk_complete_rq() directly without decrementing the request reference count. The leaked reference count incorrectly allows user copy and zero copy operations on the completed ublk request. It also triggers the WARN_ON_ONCE(refcount_read(&io->ref)) warnings in ublk_queue_reinit() and ublk_deinit_queue(). Commit c5c5eb24ed61 ("ublk: avoid ublk_io_release() called after ublk char dev is closed") already fixed the issue for ublk devices using UBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference count leak also affects UBLK_F_USER_COPY, the other reference-counted data copy mode. Fix the condition in ublk_check_and_reset_active_ref() to include all reference-counted data copy modes. This ensures that any ublk requests still owned by the ublk server when it exits have their reference counts reset to 0.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e63d2228ef831af36f963b3ab8604160cfff84c1 , < 13456b4f1033d911f8bf3a0a1195656f293ba0f6 (git)
Affected: e63d2228ef831af36f963b3ab8604160cfff84c1 , < daa24603d9f0808929514ee62ced30052ca7221c (git)
Affected: e537193fc4a43b48ac51cc6366319e15e32dd540 (git)
Affected: 6.14.6 , < 6.15 (semver)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.3 , ≤ 6.18.* (semver)
Unaffected: 6.19 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/ublk_drv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "13456b4f1033d911f8bf3a0a1195656f293ba0f6",
              "status": "affected",
              "version": "e63d2228ef831af36f963b3ab8604160cfff84c1",
              "versionType": "git"
            },
            {
              "lessThan": "daa24603d9f0808929514ee62ced30052ca7221c",
              "status": "affected",
              "version": "e63d2228ef831af36f963b3ab8604160cfff84c1",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e537193fc4a43b48ac51cc6366319e15e32dd540",
              "versionType": "git"
            },
            {
              "lessThan": "6.15",
              "status": "affected",
              "version": "6.14.6",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/ublk_drv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.3",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.14.6",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nublk: clean up user copy references on ublk server exit\n\nIf a ublk server process releases a ublk char device file, any requests\ndispatched to the ublk server but not yet completed will retain a ref\nvalue of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 (\"ublk: simplify\naborting ublk request\"), __ublk_fail_req() would decrement the reference\ncount before completing the failed request. However, that commit\noptimized __ublk_fail_req() to call __ublk_complete_rq() directly\nwithout decrementing the request reference count.\nThe leaked reference count incorrectly allows user copy and zero copy\noperations on the completed ublk request. It also triggers the\nWARN_ON_ONCE(refcount_read(\u0026io-\u003eref)) warnings in ublk_queue_reinit()\nand ublk_deinit_queue().\nCommit c5c5eb24ed61 (\"ublk: avoid ublk_io_release() called after ublk\nchar dev is closed\") already fixed the issue for ublk devices using\nUBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference\ncount leak also affects UBLK_F_USER_COPY, the other reference-counted\ndata copy mode. Fix the condition in ublk_check_and_reset_active_ref()\nto include all reference-counted data copy modes. This ensures that any\nublk requests still owned by the ublk server when it exits have their\nreference counts reset to 0."
        }
      ],
      "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 - Exploitation uses local close, io_uring, and pread/pwrite operations on a ublk character device; no network or physical path reaches the flaw.\nAC:L - A malicious server can control the outstanding I/O, server exit, request generation, and concurrent copy/commit operations. It can park the dispatch task or stall user copying, so the relevant race does not depend on uncontrollable conditions.\nPR:L - The data-plane open/read/write path has no capability check and explicitly supports non-CAP_SYS_ADMIN daemon tasks when device-node access is delegated. Device provisioning and recovery require initial-namespace CAP_SYS_ADMIN, but a low-privileged daemon account can exploit an already managed USER_COPY device.\nUI:N - The attacker can generate the necessary block I/O and server shutdown/recovery sequence without another user\u0027s action.\nS:U - The vulnerable ublk code and the affected kernel memory and execution context belong to the same kernel security authority.\nC:H - The stale reference can permit a copy before dispatch resets the refcount, after which concurrent completion can free or reuse bio, bvec, and request pages still being traversed. A pread operation can therefore disclose broadly controllable freed or reallocated kernel-backed memory.\nI:H - A concurrent pwrite can operate through freed or attacker-groomed bio/bvec state, providing a path to corrupt reused pages or redirect writes to kernel memory and potentially hijack control flow.\nA:H - The resulting use-after-free can cause an oops or kernel panic, and the deterministic WARN_ON_ONCE sites can also panic systems configured with panic-on-warn."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:11:51.227Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/13456b4f1033d911f8bf3a0a1195656f293ba0f6"
        },
        {
          "url": "https://git.kernel.org/stable/c/daa24603d9f0808929514ee62ced30052ca7221c"
        }
      ],
      "title": "ublk: clean up user copy references on ublk server exit",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71070",
    "datePublished": "2026-01-13T15:31:24.709Z",
    "dateReserved": "2026-01-13T15:30:19.647Z",
    "dateUpdated": "2026-08-05T12:11:51.227Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-71070",
      "date": "2026-09-17",
      "epss": "0.00141",
      "percentile": "0.03809"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-71070\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-01-13T16:16:06.413\",\"lastModified\":\"2026-07-30T06:24:48.753\",\"vulnStatus\":\"Deferred\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nublk: clean up user copy references on ublk server exit\\n\\nIf a ublk server process releases a ublk char device file, any requests\\ndispatched to the ublk server but not yet completed will retain a ref\\nvalue of UBLK_REFCOUNT_INIT. Before commit e63d2228ef83 (\\\"ublk: simplify\\naborting ublk request\\\"), __ublk_fail_req() would decrement the reference\\ncount before completing the failed request. However, that commit\\noptimized __ublk_fail_req() to call __ublk_complete_rq() directly\\nwithout decrementing the request reference count.\\nThe leaked reference count incorrectly allows user copy and zero copy\\noperations on the completed ublk request. It also triggers the\\nWARN_ON_ONCE(refcount_read(\u0026io-\u003eref)) warnings in ublk_queue_reinit()\\nand ublk_deinit_queue().\\nCommit c5c5eb24ed61 (\\\"ublk: avoid ublk_io_release() called after ublk\\nchar dev is closed\\\") already fixed the issue for ublk devices using\\nUBLK_F_SUPPORT_ZERO_COPY or UBLK_F_AUTO_BUF_REG. However, the reference\\ncount leak also affects UBLK_F_USER_COPY, the other reference-counted\\ndata copy mode. Fix the condition in ublk_check_and_reset_active_ref()\\nto include all reference-counted data copy modes. This ensures that any\\nublk requests still owned by the ublk server when it exits have their\\nreference counts reset to 0.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nublk: limpiar referencias de copia de usuario al salir el servidor ublk\\n\\nSi un proceso de servidor ublk libera un archivo de dispositivo de caracteres ublk, cualquier solicitud despachada al servidor ublk pero a\u00fan no completada retendr\u00e1 un valor de referencia de UBLK_REFCOUNT_INIT. Antes del commit e63d2228ef83 (\u0027ublk: simplificar la anulaci\u00f3n de solicitud ublk\u0027), __ublk_fail_req() decrementar\u00eda el contador de referencias antes de completar la solicitud fallida. Sin embargo, ese commit optimiz\u00f3 __ublk_fail_req() para llamar directamente a __ublk_complete_rq() sin decrementar el contador de referencias de la solicitud.\\nEl contador de referencias filtrado permite incorrectamente operaciones de copia de usuario y copia cero en la solicitud ublk completada. Tambi\u00e9n activa las advertencias WARN_ON_ONCE(refcount_read(\u0026amp;io-\u0026gt;ref)) en ublk_queue_reinit() y ublk_deinit_queue().\\nEl commit c5c5eb24ed61 (\u0027ublk: evitar que se llame a ublk_io_release() despu\u00e9s de cerrar el dispositivo de caracteres ublk\u0027) ya solucion\u00f3 el problema para dispositivos ublk que utilizan UBLK_F_SUPPORT_ZERO_COPY o UBLK_F_AUTO_BUF_REG. Sin embargo, la fuga del contador de referencias tambi\u00e9n afecta a UBLK_F_USER_COPY, el otro modo de copia de datos con contador de referencias. Corregir la condici\u00f3n en ublk_check_and_reset_active_ref() para incluir todos los modos de copia de datos con contador de referencias. Esto asegura que cualquier solicitud ublk a\u00fan propiedad del servidor ublk cuando este sale tenga sus contadores de referencias restablecidos a 0.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"drivers/block/ublk_drv.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"e63d2228ef831af36f963b3ab8604160cfff84c1\",\"lessThan\":\"13456b4f1033d911f8bf3a0a1195656f293ba0f6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e63d2228ef831af36f963b3ab8604160cfff84c1\",\"lessThan\":\"daa24603d9f0808929514ee62ced30052ca7221c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"e537193fc4a43b48ac51cc6366319e15e32dd540\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6.14.6\",\"lessThan\":\"6.15\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"drivers/block/ublk_drv.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.3\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.19\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/13456b4f1033d911f8bf3a0a1195656f293ba0f6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/daa24603d9f0808929514ee62ced30052ca7221c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-14T18:51:22+00:00",
      "cve": "CVE-2025-71070",
      "id": "CVE-2025-71070",
      "initial_release_date": "2025-01-01T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ublk: clean up user copy references on ublk server exit",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-71070.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-29T01:11:28Z",
      "cve": "CVE-2025-71070",
      "id": "CVE-2025-71070",
      "initial_release_date": "2026-01-14T00:26:00Z",
      "product_status:known_not_affected": "436",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-71070",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-71070.json",
      "version": "11"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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