Vulnerability-Lookup

FKIE_CVE-2026-90036

Vulnerability from fkie_nvd - Published: 2026-09-16 11:17 - Updated: 2026-09-16 15:18

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: 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.

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "cd489b03587378645fe0d20142a33f1ed60bac98",
              "status": "affected",
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "versionType": "git"
            },
            {
              "lessThan": "6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0",
              "status": "affected",
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "versionType": "git"
            },
            {
              "lessThan": "9026932ac8be4d0ae01db47f23619a98cc57b671",
              "status": "affected",
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "versionType": "git"
            }
          ]
        },
        {
          "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": "4.9"
            },
            {
              "lessThan": "4.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "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-\u003eblocked_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\u0027s 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-\u003eblocked_locks_lock, and skip clients already expiring, whose\nblocked locks __destroy_client() frees while holding an owner\nreference. Take nn-\u003eclient_lock outside nn-\u003eblocked_locks_lock.\nEvery other site holds nn-\u003eblocked_locks_lock as a leaf, acquiring\nno further lock, so placing nn-\u003eclient_lock outside it cannot form\na lock-order cycle."
    }
  ],
  "id": "CVE-2026-90036",
  "lastModified": "2026-09-16T15:18:26.420",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-16T11:17:16.803",
  "references": [
    {
      "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/9026932ac8be4d0ae01db47f23619a98cc57b671"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-90036 (GCVE-0-2026-90036)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:33 – Updated: 2026-09-16 14:41

Title

NFSD: Prevent client use-after-free during blocked-lock reaping

Summary

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/cd489b03587378645…
https://git.kernel.org/stable/c/6fedb2eaff77554ca…
https://git.kernel.org/stable/c/9026932ac8be4d0ae…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b , < cd489b03587378645fe0d20142a33f1ed60bac98 (git) Affected: 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b , < 6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0 (git) Affected: 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b , < 9026932ac8be4d0ae01db47f23619a98cc57b671 (git)
Linux	Linux	Affected: 4.9 Unaffected: 0 , < 4.9 (semver) Unaffected: 6.18.51 , ≤ 6.18.* (semver) Unaffected: 7.2.5 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "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",
          "versions": [
            {
              "lessThan": "cd489b03587378645fe0d20142a33f1ed60bac98",
              "status": "affected",
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "versionType": "git"
            },
            {
              "lessThan": "6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0",
              "status": "affected",
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "versionType": "git"
            },
            {
              "lessThan": "9026932ac8be4d0ae01db47f23619a98cc57b671",
              "status": "affected",
              "version": "7919d0a27f1e7cb324e023776aa1cbff00f1ee7b",
              "versionType": "git"
            }
          ]
        },
        {
          "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": "4.9"
            },
            {
              "lessThan": "4.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.51",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.51",
                  "versionStartIncluding": "4.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.5",
                  "versionStartIncluding": "4.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "4.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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-\u003eblocked_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\u0027s 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-\u003eblocked_locks_lock, and skip clients already expiring, whose\nblocked locks __destroy_client() frees while holding an owner\nreference. Take nn-\u003eclient_lock outside nn-\u003eblocked_locks_lock.\nEvery other site holds nn-\u003eblocked_locks_lock as a leaf, acquiring\nno further lock, so placing nn-\u003eclient_lock outside it cannot form\na lock-order cycle."
        }
      ],
      "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 is the in-kernel NFS server; the UAF is reached by remote NFSv4.1 COMPOUND RPCs over TCP/UDP 2049 (EXCHANGE_ID, CREATE_SESSION, OPEN, blocking LOCK, DESTROY_SESSION, DESTROY_CLIENTID) that queue a blocked lock and expire the client while nfs4_laundromat() reaps it.\nAC:L - The attacker controls both sides: one client holds a conflicting lock while another queues a FILE_LOCK_DEFERRED blocked lock (bare lockowner), then DESTROY_CLIENTID races with laundromat free_blocked_lock() after nbl detach; concurrent compounds create the race and it is retryable.\nPR:N - Typical nfsd deployments use AUTH_SYS/AUTH_NULL with no cryptographic RPC authentication. A remote peer that can reach an export can create NFSv4.1 state and issue DESTROY_CLIENTID (ALLOWED_WITHOUT_FH) without a local account or kernel capabilities on the server.\nUI:N - Exploitation requires only attacker-sent NFS RPCs against a running nfsd export. No victim user action such as mounting a filesystem or opening a local file on the server is required.\nS:U - The use-after-free is of struct nfs4_client in the NFS server kernel and does not cross a separate security authority such as a VM, guest/host, sandbox, or IOMMU boundary.\nC:H - free_blocked_lock() drops flc_owner into nfs4_put_stateowner(), which takes cl_lock on a nfs4_client already freed by concurrent expire_client(). The mergeable client_slab object (KMEM_CACHE flags 0) can be reclaimed via EXCHANGE_ID to disclose kernel memory.\nI:H - nfs4_put_stateowner() does atomic_dec_and_lock on the freed client\u0027s cl_lock and so_unhash walks client-owned lists; reclaiming the nfs4_client slab enables heap corruption and control-flow hijack. Kernel guidance scores use-after-free as I:H.\nA:H - Use-after-free of nfs4_client (spin_lock of freed cl_lock) in the laundromat worker oopses or panics the NFS server even without full exploitation, fully denying service of the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-16T14:41:47.831Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98"
        },
        {
          "url": "https://git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0"
        },
        {
          "url": "https://git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671"
        }
      ],
      "title": "NFSD: Prevent client use-after-free during blocked-lock reaping",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90036",
    "datePublished": "2026-09-16T10:33:35.967Z",
    "dateReserved": "2026-09-11T19:38:34.782Z",
    "dateUpdated": "2026-09-16T14:41:47.831Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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