{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "e6f7e1487ab528a6c653bd0d42812ff2942846cd"
            },
            {
              "fixed": "763c0bad872368304db718f79af7e93048885c67"
            },
            {
              "fixed": "559570f91a7d4d199a72105e4980bef791f4cbf1"
            },
            {
              "fixed": "58884694978a3d7d111edb433d7fd6a6c5af2f34"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "986a21ace186433e0397a59491646edad8c8d636"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        },
        {
          "events": [
            {
              "introduced": "6.15.3"
            },
            {
              "fixed": "6.16"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.16.0"
            },
            {
              "fixed": "6.18.50"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89670.json"
  },
  "details": "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 -\u003e call_rcu()\n                                      /* grace period elapses;\n                                         slab page recycled */\n    nfsd_file_get(new)\n      refcount_inc_not_zero(\u0026new-\u003enf_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-\u003enf_net and new-\u003enf_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.",
  "id": "CVE-2026-89670",
  "modified": "2026-09-15T03:30:59.451615632Z",
  "published": "2026-09-11T19:45:55.846Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/559570f91a7d4d199a72105e4980bef791f4cbf1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/58884694978a3d7d111edb433d7fd6a6c5af2f34"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/763c0bad872368304db718f79af7e93048885c67"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89670.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89670"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "nfsd: hold rcu across localio cmpxchg retry"
}