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

Vulnerability from cvelistv5 – Published: 2026-09-17 16:06 – Updated: 2026-10-21 12:50
VLAI
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 CNA under the mitre root
CNA scorecard D 53/100 over 7061 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 336b6da10021c69a8f273bbacdf7432fdc89a06f (git)
Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 5527af72b0100c94287bfec901b6313eeac567ca (git)
Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 163c16e01f53fc8eb8d0f3484ae6c382265ecbbd (git)
Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 436a214514e24103159aea455147d58b44a8a585 (git)
Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.12
Unaffected: 0 , < 4.12 (semver)
Unaffected: 6.6.160 , ≤ 6.6.* (semver)
Unaffected: 6.12.114 , ≤ 6.12.* (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "programFiles": [
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      "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."
        }
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            "version": "3.1"
          },
          "scenarios": [
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              "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."
            }
          ]
        }
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      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:50:06.603Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc"
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      "title": "NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers",
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    "cveId": "CVE-2026-90149",
    "datePublished": "2026-09-17T16:06:43.671Z",
    "dateReserved": "2026-09-11T19:38:34.789Z",
    "dateUpdated": "2026-10-21T12:50:06.603Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-10-23",
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            "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."
          }
        ],
        "id": "CVE-2026-90149",
        "lastModified": "2026-10-21T13:20:40.177",
        "metrics": {
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              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 7.5,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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        "vulnStatus": "Received"
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    "redhat_vex": {
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      "current_release_date": "2026-10-13T14:36:17+00:00",
      "cve": "CVE-2026-90149",
      "id": "CVE-2026-90149",
      "initial_release_date": "2026-09-17T00:00:00+00:00",
      "product_status:known_affected": "263",
      "product_status:known_not_affected": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-90149.json",
      "version": "3"
    },
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      "aggregate_severity": "moderate",
      "current_release_date": "2026-10-20T00:45:38Z",
      "cve": "CVE-2026-90149",
      "id": "CVE-2026-90149",
      "initial_release_date": "2026-09-22T16:30:14Z",
      "product_status:known_affected": "671",
      "product_status:known_not_affected": "6",
      "product_status:recommended": "212",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-90149",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-90149.json",
      "version": "10"
    }
  }
}



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