CVE-2026-64259 (GCVE-0-2026-64259)
Vulnerability from cvelistv5
Published
2026-07-25 08:49
Modified
2026-08-17 04:52
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: fuse-uring: make a fuse_req on SQE commit only findable after memcpy Bad userspace might try to trick us and send commit SQEs request unique / commit-id of requests that are not even send to fuse-server (io_uring_cmd_done() not called) yet. fuse_uring_commit_fetch() ends the fuse request when the ring entry has a wrong state, but that could have caused a use-after-free with the memcpy operations in fuse_uring_send_in_task(). In order to avoid such races the call of fuse_uring_add_to_pq() is moved after the copy operations and just before completing the io-uring request - malicious userspace cannot find the request anymore until all prepration work in fuse-client/kernel is completed. This also moves fuse_uring_add_to_pq() a bit up in the code to avoid a forward declaration. Also not with a preparation commit, to make it easier to back port to older kernels.
References
Impacted products
Vendor Product Version
Linux Linux Version: c090c8abae4b6b77a1bee116aa6c385456ebef96
Version: c090c8abae4b6b77a1bee116aa6c385456ebef96
Version: c090c8abae4b6b77a1bee116aa6c385456ebef96
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/dev_uring.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "e1711479e9068ea31b31353a702a51e639c3d059",
              "status": "affected",
              "version": "c090c8abae4b6b77a1bee116aa6c385456ebef96",
              "versionType": "git"
            },
            {
              "lessThan": "a635f427d57e2012102ae4886b48d8955c59fb86",
              "status": "affected",
              "version": "c090c8abae4b6b77a1bee116aa6c385456ebef96",
              "versionType": "git"
            },
            {
              "lessThan": "1efd3d474fc0ba74dfd984249bca78807d739812",
              "status": "affected",
              "version": "c090c8abae4b6b77a1bee116aa6c385456ebef96",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/dev_uring.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": "6.18.*",
              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.39",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.4",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse-uring: make a fuse_req on SQE commit only findable after memcpy\n\nBad userspace might try to trick us and send commit SQEs request\nunique / commit-id of requests that are not even send to\nfuse-server (io_uring_cmd_done() not called) yet.\n\nfuse_uring_commit_fetch() ends the fuse request when the ring entry\nhas a wrong state, but that could have caused a use-after-free\nwith the memcpy operations in fuse_uring_send_in_task().\nIn order to avoid such races the call of fuse_uring_add_to_pq()\nis moved after the copy operations and just before completing\nthe io-uring request - malicious userspace cannot find the request\nanymore until all prepration work in fuse-client/kernel is completed.\n\nThis also moves fuse_uring_add_to_pq() a bit up in the code to\navoid a forward declaration. Also not with a preparation commit,\nto make it easier to back port to older kernels."
        }
      ],
      "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 - Triggering requires local filesystem operations and IORING_OP_URING_CMD submissions on an associated /dev/fuse descriptor. Network peers cannot directly reach this commit path.\nAC:L - The attacker controls request generation, predictable sequential commit IDs, concurrent commit submission, and deferred io_uring task-work execution. Both sides of the race are attacker-controlled.\nPR:L - An ordinary user can create and operate a FUSE mount through fusermount or CAP_SYS_ADMIN in a user namespace; FUSE permits user-namespace mounts and this path has no init-namespace capability check.\nUI:N - The attacker can operate both the FUSE daemon and a client thread that generates requests, requiring no victim action.\nS:U - Exploitation compromises the host kernel within the same security authority and does not cross a VM, IOMMU, or comparable boundary.\nC:H - The freed request\u0027s argument pointers and copy sources are dereferenced while copying into attacker-controlled ring memory. Heap reclamation can therefore expose sensitive kernel memory.\nI:H - The use-after-free performs writes to reclaimed request memory through embedded spinlocks and request flags, providing exploitable heap corruption that may enable arbitrary writes or kernel code execution.\nA:H - The dangling request can cause invalid dereferences, corrupted request state, double completion, hangs, or a kernel panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:52:12.445Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e1711479e9068ea31b31353a702a51e639c3d059"
        },
        {
          "url": "https://git.kernel.org/stable/c/a635f427d57e2012102ae4886b48d8955c59fb86"
        },
        {
          "url": "https://git.kernel.org/stable/c/1efd3d474fc0ba74dfd984249bca78807d739812"
        }
      ],
      "title": "fuse-uring: make a fuse_req on SQE commit only findable after memcpy",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64259",
    "datePublished": "2026-07-25T08:49:10.756Z",
    "dateReserved": "2026-07-19T15:36:31.773Z",
    "dateUpdated": "2026-08-17T04:52:12.445Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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