{"id":"CVE-2026-90149","state":"PUBLISHED","title":"NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers","description":"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->cl_session is NULL; it uses clp->cl_slot_tbl), so\nI/O to a v4.0 flexfiles DS oopses:\n\n  - nfs4_init_ds_session() dereferences clp->cl_session->session_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->cl_session->fc_slot_table on every DS I/O error. Fall back to the\n    v4.0 transport slot table (clp->cl_slot_tbl) when there is no session.","publishedAt":"2026-09-17T16:06:43.671Z","updatedAt":"2026-10-30T12:34:23.855Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"e55d7fec8a9290f73032ee34c35dd68532809633","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"336b6da10021c69a8f273bbacdf7432fdc89a06f","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"5527af72b0100c94287bfec901b6313eeac567ca","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"163c16e01f53fc8eb8d0f3484ae6c382265ecbbd","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"436a214514e24103159aea455147d58b44a8a585","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/flexfilelayout/flexfilelayout.c","fs/nfs/nfs4session.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.12","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/flexfilelayout/flexfilelayout.c","fs/nfs/nfs4session.c"]}],"references":["https://git.kernel.org/stable/c/e55d7fec8a9290f73032ee34c35dd68532809633","https://git.kernel.org/stable/c/336b6da10021c69a8f273bbacdf7432fdc89a06f","https://git.kernel.org/stable/c/5527af72b0100c94287bfec901b6313eeac567ca","https://git.kernel.org/stable/c/163c16e01f53fc8eb8d0f3484ae6c382265ecbbd","https://git.kernel.org/stable/c/436a214514e24103159aea455147d58b44a8a585","https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc"],"weaknesses":[],"ingestedAt":"2026-10-30T12:54:04.478Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/90xxx/CVE-2026-90149.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-90149","state":"PUBLISHED","datePublished":"2026-09-17T16:06:43.671Z","dateUpdated":"2026-10-30T12:34:23.855Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.789Z"},"containers":{"cna":{"title":"NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers","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->cl_session is NULL; it uses clp->cl_slot_tbl), so\nI/O to a v4.0 flexfiles DS oopses:\n\n  - nfs4_init_ds_session() dereferences clp->cl_session->session_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->cl_session->fc_slot_table on every DS I/O error. Fall back to the\n    v4.0 transport slot table (clp->cl_slot_tbl) when there is no session."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"e55d7fec8a9290f73032ee34c35dd68532809633","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"336b6da10021c69a8f273bbacdf7432fdc89a06f","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"5527af72b0100c94287bfec901b6313eeac567ca","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"163c16e01f53fc8eb8d0f3484ae6c382265ecbbd","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"436a214514e24103159aea455147d58b44a8a585","versionType":"git"},{"version":"a7878ca140084ec267ede48fce64d7e60f6d873e","status":"affected","lessThan":"2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/flexfilelayout/flexfilelayout.c","fs/nfs/nfs4session.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.12","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/flexfilelayout/flexfilelayout.c","fs/nfs/nfs4session.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e55d7fec8a9290f73032ee34c35dd68532809633"},{"url":"https://git.kernel.org/stable/c/336b6da10021c69a8f273bbacdf7432fdc89a06f"},{"url":"https://git.kernel.org/stable/c/5527af72b0100c94287bfec901b6313eeac567ca"},{"url":"https://git.kernel.org/stable/c/163c16e01f53fc8eb8d0f3484ae6c382265ecbbd"},{"url":"https://git.kernel.org/stable/c/436a214514e24103159aea455147d58b44a8a585"},{"url":"https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"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 && minor_version<3). The MDS sets those two GETDEVICEINFO XDR words, and the next read/write that reaches nfs4_ff_layout_prepare_ds() → 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->cl_session->session_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->fc_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->fc_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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:34:23.855Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}