CVE-2026-89688 (GCVE-0-2026-89688)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
Modified
2026-10-19 08:51
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: drop the stateid, not the stateowner, on seqid_op replay retry In nfs4_preprocess_seqid_op() the stateid is obtained from nfsd4_lookup_stateid(), which holds a reference on the nfs4_stid (sc_count) but takes no reference on the stateowner. openlockstateid() merely casts that stid and likewise takes no reference. When nfsd4_cstate_assign_replay() returns -EAGAIN (the replay owner is being torn down, RP_UNHASHED) it has not taken a stateowner reference on that path. The error handling nevertheless called nfs4_put_stateowner(stp->st_stateowner), dropping an so_count reference the function never acquired -- risking a stateowner refcount underflow and use-after-free -- while leaking the sc_count reference held on the stid. The leaked stid reference can also stall a concurrent nfsd4_close_open_stateid() waiting for sc_count to drop. Drop the reference actually held -- the stid -- before retrying. The stateowner stays alive through the reference held by the stid. This mirrors the open path in nfsd4_process_open1(), where the put balances a reference that path explicitly holds on the stateowner.
References
Impacted products
Vendor Product Version
Linux Linux Version: eec7620800081e27dbf8019ac2e66259f0d5bf6f
Version: eec7620800081e27dbf8019ac2e66259f0d5bf6f
Version: eec7620800081e27dbf8019ac2e66259f0d5bf6f
Version: eec7620800081e27dbf8019ac2e66259f0d5bf6f
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.10"
            },
            {
              "lessThan": "6.10",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.109",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: drop the stateid, not the stateowner, on seqid_op replay retry\n\nIn nfs4_preprocess_seqid_op() the stateid is obtained from\nnfsd4_lookup_stateid(), which holds a reference on the nfs4_stid\n(sc_count) but takes no reference on the stateowner. openlockstateid()\nmerely casts that stid and likewise takes no reference.\n\nWhen nfsd4_cstate_assign_replay() returns -EAGAIN (the replay owner is\nbeing torn down, RP_UNHASHED) it has not taken a stateowner reference on\nthat path. The error handling nevertheless called\nnfs4_put_stateowner(stp-\u003est_stateowner), dropping an so_count reference\nthe function never acquired -- risking a stateowner refcount underflow and\nuse-after-free -- while leaking the sc_count reference held on the stid.\nThe leaked stid reference can also stall a concurrent\nnfsd4_close_open_stateid() waiting for sc_count to drop.\n\nDrop the reference actually held -- the stid -- before retrying. The\nstateowner stays alive through the reference held by the stid. This mirrors\nthe open path in nfsd4_process_open1(), where the put balances a reference\nthat path explicitly holds on the stateowner."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - nfsd processes NFSv4 COMPOUND ops (CLOSE, OPEN_DOWNGRADE, LOCK, OPEN_CONFIRM) in the in-kernel NFS server on TCP/UDP 2049; those handlers call nfs4_preprocess_seqid_op(), so a remote peer reaches the bug with no local access.\nAC:L - A remote NFSv4.0 client drives both sides by sending concurrent CLOSE and another seqid-mutating op on the same openowner; CLOSE\u0027s move_to_close_lru() sets RP_UNHASHED and waits on sc_count, so the window is attacker-controlled and retryable.\nPR:N - Typical nfsd exports use AUTH_SYS/AUTH_NULL, so RPC uids are self-asserted and not cryptographically verified; any host allowed by the export list can SETCLIENTID, OPEN, then CLOSE/OPEN_DOWNGRADE with no local Linux account.\nUI:N - The attacker issues the NFSv4 COMPOUND requests itself; no victim on the server must mount a filesystem, open a file, or take any other action.\nS:U - The underflow frees an nfsd nfs4_stateowner in the NFS server kernel; impact stays in that kernel and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - nfs4_put_stateowner() drops an so_count the seqid path never took, freeing the stateowner while the stid and retry loop still use it; that UAF enables slab reclaim and kernel memory disclosure.\nI:H - The same UAF exposes so_ops-\u003eso_unhash/so_free function pointers and list writes under cl_lock, yielding a kernel write and control-flow hijack primitive.\nA:H - The UAF oopses or panics nfsd; the leaked stid sc_count also leaves move_to_close_lru() waiting forever for sc_count==2, hanging an nfsd thread, and the -EAGAIN retry can spin while RP_UNHASHED stays set."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:51:01.558Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/69ed78b6b947c9257213164678b4edf17533093b"
        },
        {
          "url": "https://git.kernel.org/stable/c/00843074d9b84824552c9679d423d29500ca5de0"
        },
        {
          "url": "https://git.kernel.org/stable/c/f7cb90ddc021747fc9abfd4cf5252d425fd34eec"
        },
        {
          "url": "https://git.kernel.org/stable/c/5e4627d3513e60accfce9d5f4c7fa95251ef93d6"
        }
      ],
      "title": "nfsd: drop the stateid, not the stateowner, on seqid_op replay retry",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89688",
    "datePublished": "2026-09-11T19:46:09.322Z",
    "dateReserved": "2026-09-11T19:38:34.749Z",
    "dateUpdated": "2026-10-19T08:51:01.558Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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