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GHSA-5PV5-P9Q3-RVV6

Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-18 18:31

Details

In the Linux kernel, the following vulnerability has been resolved:

NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers

flexfiles accepts NFSv4.0 data servers, but two NFSv4 code paths assume the data server client has a session. Unlike NFSv4.1+, an NFSv4.0 client has no session (clp->cl_session is NULL; it uses clp->cl_slot_tbl), so I/O to a v4.0 flexfiles DS oopses:

nfs4_init_ds_session() dereferences clp->cl_session->session_state while seeding the DS lease. It also only seeds cl_lease_time when NFS4_SESSION_INITING is set; without a session that never happens, so cl_lease_time stays 0 and nfs4_renew_state() busy-loops, requeuing every 5 seconds. Seed the lease whenever there is no session and return before touching session state.
ff_layout_async_handle_error_v4() dereferences clp->cl_session->fc_slot_table on every DS I/O error. Fall back to the v4.0 transport slot table (clp->cl_slot_tbl) when there is no session.

Severity

7.5 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-90149"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-17T17:17:07Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers\n\nflexfiles accepts NFSv4.0 data servers, but two NFSv4 code paths assume\nthe data server client has a session. Unlike NFSv4.1+, an NFSv4.0 client\nhas no session (clp-\u003ecl_session is NULL; it uses clp-\u003ecl_slot_tbl), so\nI/O to a v4.0 flexfiles DS oopses:\n\n  - nfs4_init_ds_session() dereferences clp-\u003ecl_session-\u003esession_state\n    while seeding the DS lease. It also only seeds cl_lease_time when\n    NFS4_SESSION_INITING is set; without a session that never happens, so\n    cl_lease_time stays 0 and nfs4_renew_state() busy-loops, requeuing\n    every 5 seconds. Seed the lease whenever there is no session and\n    return before touching session state.\n\n  - ff_layout_async_handle_error_v4() dereferences\n    clp-\u003ecl_session-\u003efc_slot_table on every DS I/O error. Fall back to the\n    v4.0 transport slot table (clp-\u003ecl_slot_tbl) when there is no session.",
  "id": "GHSA-5pv5-p9q3-rvv6",
  "modified": "2026-09-18T18:31:27Z",
  "published": "2026-09-17T18:31:52Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90149"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/163c16e01f53fc8eb8d0f3484ae6c382265ecbbd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/436a214514e24103159aea455147d58b44a8a585"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-90149 (GCVE-0-2026-90149)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:06 – Updated: 2026-09-18 17:53

Title

NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers

Summary

In the Linux kernel, the following vulnerability has been resolved: NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers flexfiles accepts NFSv4.0 data servers, but two NFSv4 code paths assume the data server client has a session. Unlike NFSv4.1+, an NFSv4.0 client has no session (clp->cl_session is NULL; it uses clp->cl_slot_tbl), so I/O to a v4.0 flexfiles DS oopses: - nfs4_init_ds_session() dereferences clp->cl_session->session_state while seeding the DS lease. It also only seeds cl_lease_time when NFS4_SESSION_INITING is set; without a session that never happens, so cl_lease_time stays 0 and nfs4_renew_state() busy-loops, requeuing every 5 seconds. Seed the lease whenever there is no session and return before touching session state. - ff_layout_async_handle_error_v4() dereferences clp->cl_session->fc_slot_table on every DS I/O error. Fall back to the v4.0 transport slot table (clp->cl_slot_tbl) when there is no session.

Severity

7.5 (High)


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

Assigner

Linux mitre root Scorecard

References

3 references

URL	Tags
https://git.kernel.org/stable/c/163c16e01f53fc8eb…
https://git.kernel.org/stable/c/436a214514e241031…
https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 163c16e01f53fc8eb8d0f3484ae6c382265ecbbd (git) Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 436a214514e24103159aea455147d58b44a8a585 (git) Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc (git)
Linux	Linux	Affected: 4.12 Unaffected: 0 , < 4.12 (semver) Unaffected: 6.18.52 , ≤ 6.18.* (semver) Unaffected: 7.2.6 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfs/flexfilelayout/flexfilelayout.c",
            "fs/nfs/nfs4session.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "163c16e01f53fc8eb8d0f3484ae6c382265ecbbd",
              "status": "affected",
              "version": "a7878ca140084ec267ede48fce64d7e60f6d873e",
              "versionType": "git"
            },
            {
              "lessThan": "436a214514e24103159aea455147d58b44a8a585",
              "status": "affected",
              "version": "a7878ca140084ec267ede48fce64d7e60f6d873e",
              "versionType": "git"
            },
            {
              "lessThan": "2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc",
              "status": "affected",
              "version": "a7878ca140084ec267ede48fce64d7e60f6d873e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfs/flexfilelayout/flexfilelayout.c",
            "fs/nfs/nfs4session.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.12"
            },
            {
              "lessThan": "4.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "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": "6.18.52",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers\n\nflexfiles accepts NFSv4.0 data servers, but two NFSv4 code paths assume\nthe data server client has a session. Unlike NFSv4.1+, an NFSv4.0 client\nhas no session (clp-\u003ecl_session is NULL; it uses clp-\u003ecl_slot_tbl), so\nI/O to a v4.0 flexfiles DS oopses:\n\n  - nfs4_init_ds_session() dereferences clp-\u003ecl_session-\u003esession_state\n    while seeding the DS lease. It also only seeds cl_lease_time when\n    NFS4_SESSION_INITING is set; without a session that never happens, so\n    cl_lease_time stays 0 and nfs4_renew_state() busy-loops, requeuing\n    every 5 seconds. Seed the lease whenever there is no session and\n    return before touching session state.\n\n  - ff_layout_async_handle_error_v4() dereferences\n    clp-\u003ecl_session-\u003efc_slot_table on every DS I/O error. Fall back to the\n    v4.0 transport slot table (clp-\u003ecl_slot_tbl) when there is no session."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - A malicious NFSv4.1 MDS sets version=4 and minor_version=0 in the flexfiles GETDEVICEINFO device-addr body; nfs4_ff_alloc_deviceid_node() accepts that pair, nfs4_set_ds_client() builds a session-less v4.0 nfs_client, and nfs4_init_ds_session() then crashes on DS connect. GETDEVICEINFO is NFS/RPC over TCP.\nAC:L - nfs4_ff_alloc_deviceid_node() explicitly allows an NFSv4.0 DS (version==4 \u0026\u0026 minor_version\u003c3). The MDS sets those two GETDEVICEINFO XDR words, and the next read/write that reaches nfs4_ff_layout_prepare_ds() \u2192 nfs4_init_ds_session() dereferences the NULL cl_session with no race.\nPR:N - The attacker is the remote MDS (or an on-path injector of GETDEVICEINFO replies) and needs no account or capability on the victim client; the client authenticates to the server, not the reverse.\nUI:N - On an already-mounted pNFS flexfiles share, ordinary file I/O drives LAYOUTGET then GETDEVICEINFO; the MDS can return a v4.0 DS in that GETDEVICEINFO and nfs4_init_ds_session() oopses with no further victim action such as mounting a new image.\nS:U - The NULL dereference oopses the NFS client kernel itself and does not cross a VM, IOMMU, or other security-authority boundary.\nC:N - nfs4_init_ds_session() loads clp-\u003ecl_session-\u003esession_state when cl_session is NULL, a pure NULL-pointer fault at a low offset of struct nfs4_session, with no out-of-bounds read or other disclosure.\nI:N - The same NULL load of cl_session (and cl_session-\u003efc_slot_table in ff_layout_async_handle_error_v4) faults before any store; this is not a UAF, overflow, or type confusion that could yield a write primitive.\nA:H - Dereferencing the NULL cl_session in nfs4_init_ds_session() on DS connect, or cl_session-\u003efc_slot_table in ff_layout_async_handle_error_v4 on a DS I/O error, produces a kernel oops that takes down the client."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:53:25.246Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/163c16e01f53fc8eb8d0f3484ae6c382265ecbbd"
        },
        {
          "url": "https://git.kernel.org/stable/c/436a214514e24103159aea455147d58b44a8a585"
        },
        {
          "url": "https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc"
        }
      ],
      "title": "NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90149",
    "datePublished": "2026-09-17T16:06:43.671Z",
    "dateReserved": "2026-09-11T19:38:34.789Z",
    "dateUpdated": "2026-09-18T17:53:25.246Z",
    "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.

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.
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GHSA-5PV5-P9Q3-RVV6

CVE-2026-90149 (GCVE-0-2026-90149)

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