CVE-2026-90149 (GCVE-0-2026-90149)
Vulnerability from cvelistv5 – Published: 2026-09-17 16:06 – Updated: 2026-10-30 12:34
VLAI
EPSS
VEX
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)
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
a7878ca140084ec267ede48fce64d7e60f6d873e , < e55d7fec8a9290f73032ee34c35dd68532809633
(git)
Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 336b6da10021c69a8f273bbacdf7432fdc89a06f (git) Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 5527af72b0100c94287bfec901b6313eeac567ca (git) Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 163c16e01f53fc8eb8d0f3484ae6c382265ecbbd (git) Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 436a214514e24103159aea455147d58b44a8a585 (git) Affected: a7878ca140084ec267ede48fce64d7e60f6d873e , < 2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc (git) |
guessed | |
| Linux | Linux |
Affected:
4.12
Unaffected: 0 , < 4.12 (semver) Unaffected: 6.1.191 , ≤ 6.1.* (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 |
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{
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"status": "unaffected",
"version": "7.2.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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"nodes": [
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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."
}
],
"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": "2026-10-30T12:34:23.855Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
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"url": "https://git.kernel.org/stable/c/e55d7fec8a9290f73032ee34c35dd68532809633"
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"url": "https://git.kernel.org/stable/c/336b6da10021c69a8f273bbacdf7432fdc89a06f"
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"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",
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"cveId": "CVE-2026-90149",
"datePublished": "2026-09-17T16:06:43.671Z",
"dateReserved": "2026-09-11T19:38:34.789Z",
"dateUpdated": "2026-10-30T12:34:23.855Z",
"state": "PUBLISHED"
},
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"date": "2026-11-14",
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"versions": [
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"descriptions": [
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"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."
}
],
"id": "CVE-2026-90149",
"lastModified": "2026-10-30T13:20:43.453",
"metrics": {
"cvssMetricV31": [
{
"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",
"version": "3.1"
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
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],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-11-06T01:31:26+00:00",
"cve": "CVE-2026-90149",
"id": "CVE-2026-90149",
"initial_release_date": "2026-09-17T00:00:00+00:00",
"product_status:known_affected": "189",
"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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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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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.
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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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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.