CVE-2026-90036

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent client use-after-free during blocked-lock reaping A bare lock owner -- its only remaining reference a blocked lock on nn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but no reference keeping the client alive. When the per-net laundromat reaps such a lock, freeing the nbl drops the owner reference held through flc_owner, and the final nfs4_put_stateowner() takes the client's cl_lock. Because the laundromat detaches the nbl first, __destroy_client() no longer finds it, so a concurrent force_expire_client() can free the client before nfs4_put_stateowner() runs, dereferencing cl_lock in freed memory. Pin the client with cl_rpc_users before dropping nn->blocked_locks_lock, and skip clients already expiring, whose blocked locks __destroy_client() frees while holding an owner reference. Take nn->client_lock outside nn->blocked_locks_lock. Every other site holds nn->blocked_locks_lock as a leaf, acquiring no further lock, so placing nn->client_lock outside it cannot form a lock-order cycle.

Severity

CRITICAL

CVSS score

9.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-16 11:17:16.803000

Last modified

2026-10-21 13:20:34.647000

View original CVE JSON

{
  "id": "CVE-2026-90036",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-16T11:17:16.803",
  "lastModified": "2026-10-21T13:20:34.647",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during blocked-lock reaping\n\nA bare lock owner -- its only remaining reference a blocked lock on\nnn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but\nno reference keeping the client alive. When the per-net laundromat\nreaps such a lock, freeing the nbl drops the owner reference\nheld through flc_owner, and the final nfs4_put_stateowner()\ntakes the client's cl_lock. Because the laundromat detaches the\nnbl first, __destroy_client() no longer finds it, so a concurrent\nforce_expire_client() can free the client before nfs4_put_stateowner()\nruns, dereferencing cl_lock in freed memory.\n\nPin the client with cl_rpc_users before dropping\nnn->blocked_locks_lock, and skip clients already expiring, whose\nblocked locks __destroy_client() frees while holding an owner\nreference. Take nn->client_lock outside nn->blocked_locks_lock.\nEvery other site holds nn->blocked_locks_lock as a leaf, acquiring\nno further lock, so placing nn->client_lock outside it cannot form\na lock-order cycle."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "lessThan": "0d53a47c913d0bce3b5ec35c28cbcca4d015f33d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "lessThan": "7081224a59a0ca4edcd62c068588f4d900199a18",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "lessThan": "cd489b03587378645fe0d20142a33f1ed60bac98",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "lessThan": "6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "lessThan": "9026932ac8be4d0ae01db47f23619a98cc57b671",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "4.9",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "4.9",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.160",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.111",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.51",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.5",
              "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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0d53a47c913d0bce3b5ec35c28cbcca4d015f33d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/7081224a59a0ca4edcd62c068588f4d900199a18",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}