{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7"
            },
            {
              "fixed": "72d40b103bb03f0124d3a3c8f71a30cbafaf6afa"
            },
            {
              "fixed": "b449b134e7762ddf98653a4b1d3e76d2d212ea64"
            },
            {
              "fixed": "f5d22e372f4ac3eb287037a488c29691d52a6330"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.14.0"
            },
            {
              "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-2026-89689.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: don't free session slots that are still in use\n\nnfsd4_sequence() can free the very slot it is currently processing.\nWhen the session shrinker has reduced se_target_maxslots below\nse_fchannel.maxreqs, the shrink path checks three conditions before\ncalling free_session_slots():\n\n  1. se_target_maxslots \u003c maxreqs  (shrink was advertised)\n  2. slot-\u003esl_generation == se_slot_gen  (slot is up-to-date)\n  3. seq-\u003emaxslots \u003c= se_target_maxslots  (client acknowledges)\n\nHowever, seq-\u003eslotid is never checked against se_target_maxslots.\nA client using a slot in the range [se_target_maxslots, maxreqs) can\nsatisfy all three conditions: its slot has the current generation\n(set by a prior SEQUENCE), and it sends sa_highest_slotid \u003c=\nse_target_maxslots to acknowledge the reduction.\n\nfree_session_slots() then kfrees every slot at index \u003e=\nse_target_maxslots, including the caller's own slot. The function\ncontinues to write sl_seqid, sl_flags, sl_generation, and stores the\ndangling pointer in cstate-\u003eslot. Later, nfsd4_store_cache_entry()\ncopies up to maxresp_cached bytes of the compound reply into the freed\nsl_data[] array, corrupting whatever slab object now occupies that\naddress.\n\nAdditionally, a concurrent thread processing SEQUENCE on a different\nhigh-numbered slot can have its slot freed out from under it.\nNFSD4_SLOT_INUSE is set under nn-\u003eclient_lock before the lock is\nreleased, so any concurrent thread past SEQUENCE will have its slot\nmarked. However, free_session_slots() does not check NFSD4_SLOT_INUSE\nbefore freeing.\n\nFix both problems by:\n 1. Checking that the current request's slotid is below the shrink\n    boundary.\n 2. Scanning slots in the to-be-freed range for NFSD4_SLOT_INUSE and\n    deferring the shrink if any are active.",
  "id": "CVE-2026-89689",
  "modified": "2026-09-15T03:30:38.602018857Z",
  "published": "2026-09-11T19:46:09.976Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/72d40b103bb03f0124d3a3c8f71a30cbafaf6afa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b449b134e7762ddf98653a4b1d3e76d2d212ea64"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f5d22e372f4ac3eb287037a488c29691d52a6330"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89689.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89689"
    },
    {
      "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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "nfsd: don't free session slots that are still in use"
}