CVE-2026-89670

{
  "id": "CVE-2026-89670",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:53.517",
  "lastModified": "2026-10-19T09:18:05.130",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: hold rcu across localio cmpxchg retry\n\nnfsd_file objects are freed via call_rcu (filecache.c:296), and\nnfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU\n(KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page\nbacking a freed nfsd_file becomes freely reclaimable once the RCU\ngrace period elapses.\n\nThe again: retry block in nfsd_open_local_fh() loads a pointer with\ncmpxchg and then calls nfsd_file_get(new) (which is\nrefcount_inc_not_zero) without holding rcu_read_lock. The sole caller\nnfs_open_local_fh() drops rcu_read_lock before invoking this helper,\nso no outer reader-side critical section covers the load.\n\n    CPU 0 (nfsd_open_local_fh)        CPU 1 (nfsd_file_put_local)\n    -----                             -----\n    new = cmpxchg(pnf, NULL, ...)\n                                      nf = xchg(pnf, NULL)\n                                      nfsd_file_put(nf)\n                                        last ref -> call_rcu()\n                                      /* grace period elapses;\n                                         slab page recycled */\n    nfsd_file_get(new)\n      refcount_inc_not_zero(&new->nf_ref)\n      /* operates on recycled memory */\n\nA non-zero word at the nf_ref offset of the recycled object makes the\nrefcount bump appear to succeed, and the caller then dereferences\nnew->nf_net and new->nf_file out of freed memory.\n\nFix by taking rcu_read_lock() immediately before the cmpxchg and\nreleasing it on all three exits of the if (new) block: the goto-again\nretry, the lost-race cleanup path, and the install-succeeded path.\nnfsd_file_put() and nfsd_net_put() stay outside the RCU section so\nthey remain free to block."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/nfsd/localio.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd",
              "lessThan": "763c0bad872368304db718f79af7e93048885c67",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd",
              "lessThan": "559570f91a7d4d199a72105e4980bef791f4cbf1",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "e6f7e1487ab528a6c653bd0d42812ff2942846cd",
              "lessThan": "58884694978a3d7d111edb433d7fd6a6c5af2f34",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "986a21ace186433e0397a59491646edad8c8d636",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "6.15.3",
              "lessThan": "6.16",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/nfsd/localio.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "6.16",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "6.16",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.50",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.4",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "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/559570f91a7d4d199a72105e4980bef791f4cbf1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}