{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "b9e8638e3d9ed8334f1f7071e081860aac37e83e"
            },
            {
              "fixed": "35f248bd40b47b229d4999581df45b97daadd977"
            },
            {
              "fixed": "311f7d926630940650447cbd1c932b076b40a6c4"
            },
            {
              "fixed": "bf4d338dc8625d70c7f2cb0657d66851a7ac9154"
            },
            {
              "fixed": "c59738a00aa51b16adc1b5ceb7c80877168efb4d"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.6.0"
            },
            {
              "fixed": "6.12.109"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.13.0"
            },
            {
              "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-2026-89696.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref\n\nWhen CONFIG_NFSD_V4_2_INTER_SSC is enabled, nfsd4_putfh() can return\nsuccess with fh_dentry and fh_export both NULL if fh_verify() returns\nnfserr_stale and putfh-\u003eno_verify is true. The NFSD4_FH_FOREIGN flag\nis set, but the compound dispatch loop only uses this flag to bypass\nthe nfserr_nofilehandle check -- it does not prevent subsequent ops\nfrom running with a NULL fh_dentry.\n\nA remote client can exploit this by crafting a COMPOUND that includes\nan inter-SSC COPY (which causes check_if_stalefh_allowed() to set\nno_verify=true on the saved PUTFH) with an additional op inserted\nbetween the source PUTFH and SAVEFH. For example, SETATTR calls\nfh_want_write() which dereferences fh_export-\u003eex_path.mnt without\ncalling fh_verify() first, causing a NULL pointer dereference in the\nnfsd kthread.\n\nFix this by gating the dispatch loop: when NFSD4_FH_FOREIGN is set\nand fh_dentry is NULL, only OP_SAVEFH (needed for the inter-SSC flow)\nand ops with ALLOWED_WITHOUT_FH (which don't need a resolved\nfilehandle) may proceed. All other ops receive nfserr_stale, per\nRFC 7862 Section 15.2.3 which specifies that foreign filehandle\nvalidation is deferred to the consuming operation and NFS4ERR_STALE\nreturned at that point.",
  "id": "CVE-2026-89696",
  "modified": "2026-09-13T03:30:30.131100154Z",
  "published": "2026-09-11T19:46:15.030Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/311f7d926630940650447cbd1c932b076b40a6c4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/35f248bd40b47b229d4999581df45b97daadd977"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bf4d338dc8625d70c7f2cb0657d66851a7ac9154"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c59738a00aa51b16adc1b5ceb7c80877168efb4d"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89696.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89696"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "nfsd: block non-SAVEFH ops after FOREIGN PUTFH to prevent NULL deref"
}