{"id":"CVE-2026-89663","state":"PUBLISHED","title":"nfsd: revoke copy-notify stateids before dropping their reference","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: revoke copy-notify stateids before dropping their reference\n\nCopy-notify stateids live in the s2s_cp_stateids IDR and on their parent\nstid's sc_cp_list, pinned by a single membership reference.\n_free_cpntf_state_locked() only unlinks an entry once its refcount reaches\nzero, so any revoke path that runs while a concurrent\nfind_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops\nthe reference without unlinking, leaving the entry discoverable with its\nmembership reference already consumed. A second revoke or a laundromat tick\nthen frees it while the reader still holds the pointer -- a\nKASAN-detectable use-after-free at the reader's nfs4_put_cpntf_state().\n\nThis affected all three revoke paths:\n\n  - The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called\n    _free_cpntf_state_locked() on the first list entry; a holder that had\n    bumped cs_count made it return early, so the next iteration\n    re-decremented and burned the holder's reference.\n\n  - OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise\n    used _free_cpntf_state_locked() and could drop 2->1 without unlinking.\n\nAdd revoke_cpntf_state_locked(), which unhashes the entry from the IDR and\nsc_cp_list first (deferring the final free to any holder), and use it from\nall three revoke paths. The drain now walks with list_for_each_entry_safe()\nand revokes each entry unconditionally, so it terminates in one pass per\nentry regardless of cs_count. The unhash is gated on\n!list_empty(&cps->cp_list); the idr_remove() gate matters because\nidr_alloc_cyclic() may have recycled the so_id by then. Keep\n_free_cpntf_state_locked() for the reference-holder put path only, where a\nconcurrent revoke may already have unlinked the entry (its list_del_init()\nthen a no-op).","publishedAt":"2026-09-11T19:45:50.577Z","updatedAt":"2026-10-19T08:50:34.792Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"06a62f6dbc60791f4229c6950b1eec6b18df9af1","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"caddbeffab1eaba1d2bcf5ceda35547863466705","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"6b8149448cdcb476fba4559d1ecc247efee9971b","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"b56d2c5f01cddbeca7d11cce81d97db4ec9a464f","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"ff8a3cff02b92b2a82f1a9876038fcf953ae9c25","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.6","versionType":"semver"},{"version":"5.10.270","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","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/nfsd/nfs4state.c"]}],"references":["https://git.kernel.org/stable/c/5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d","https://git.kernel.org/stable/c/06a62f6dbc60791f4229c6950b1eec6b18df9af1","https://git.kernel.org/stable/c/a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3","https://git.kernel.org/stable/c/caddbeffab1eaba1d2bcf5ceda35547863466705","https://git.kernel.org/stable/c/6b8149448cdcb476fba4559d1ecc247efee9971b","https://git.kernel.org/stable/c/b56d2c5f01cddbeca7d11cce81d97db4ec9a464f","https://git.kernel.org/stable/c/ff8a3cff02b92b2a82f1a9876038fcf953ae9c25","https://git.kernel.org/stable/c/3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89663.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89663","state":"PUBLISHED","datePublished":"2026-09-11T19:45:50.577Z","dateUpdated":"2026-10-19T08:50:34.792Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.744Z"},"containers":{"cna":{"title":"nfsd: revoke copy-notify stateids before dropping their reference","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: revoke copy-notify stateids before dropping their reference\n\nCopy-notify stateids live in the s2s_cp_stateids IDR and on their parent\nstid's sc_cp_list, pinned by a single membership reference.\n_free_cpntf_state_locked() only unlinks an entry once its refcount reaches\nzero, so any revoke path that runs while a concurrent\nfind_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops\nthe reference without unlinking, leaving the entry discoverable with its\nmembership reference already consumed. A second revoke or a laundromat tick\nthen frees it while the reader still holds the pointer -- a\nKASAN-detectable use-after-free at the reader's nfs4_put_cpntf_state().\n\nThis affected all three revoke paths:\n\n  - The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called\n    _free_cpntf_state_locked() on the first list entry; a holder that had\n    bumped cs_count made it return early, so the next iteration\n    re-decremented and burned the holder's reference.\n\n  - OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise\n    used _free_cpntf_state_locked() and could drop 2->1 without unlinking.\n\nAdd revoke_cpntf_state_locked(), which unhashes the entry from the IDR and\nsc_cp_list first (deferring the final free to any holder), and use it from\nall three revoke paths. The drain now walks with list_for_each_entry_safe()\nand revokes each entry unconditionally, so it terminates in one pass per\nentry regardless of cs_count. The unhash is gated on\n!list_empty(&cps->cp_list); the idr_remove() gate matters because\nidr_alloc_cyclic() may have recycled the so_id by then. Keep\n_free_cpntf_state_locked() for the reference-holder put path only, where a\nconcurrent revoke may already have unlinked the entry (its list_del_init()\nthen a no-op)."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"06a62f6dbc60791f4229c6950b1eec6b18df9af1","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"caddbeffab1eaba1d2bcf5ceda35547863466705","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"6b8149448cdcb476fba4559d1ecc247efee9971b","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"b56d2c5f01cddbeca7d11cce81d97db4ec9a464f","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"ff8a3cff02b92b2a82f1a9876038fcf953ae9c25","versionType":"git"},{"version":"624322f1adc58acd0b69f77a6ddc764207e97241","status":"affected","lessThan":"3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfsd/nfs4state.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.6","versionType":"semver"},{"version":"5.10.270","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","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/nfsd/nfs4state.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d"},{"url":"https://git.kernel.org/stable/c/06a62f6dbc60791f4229c6950b1eec6b18df9af1"},{"url":"https://git.kernel.org/stable/c/a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3"},{"url":"https://git.kernel.org/stable/c/caddbeffab1eaba1d2bcf5ceda35547863466705"},{"url":"https://git.kernel.org/stable/c/6b8149448cdcb476fba4559d1ecc247efee9971b"},{"url":"https://git.kernel.org/stable/c/b56d2c5f01cddbeca7d11cce81d97db4ec9a464f"},{"url":"https://git.kernel.org/stable/c/ff8a3cff02b92b2a82f1a9876038fcf953ae9c25"},{"url":"https://git.kernel.org/stable/c/3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The flaw is in the in-kernel NFS server (nfsd); COPY_NOTIFY, READ using a copy-notify stateid, CLOSE, and OFFLOAD_CANCEL are processed from NFSv4.2 compounds over TCP/2049, so a remote NFS client reaches the use-after-free over the network.\nAC:L - A malicious client fully controls both sides of the race: one compound READs with the copy-notify stateid so find_cpntf_state holds a cs_count reference while a concurrent CLOSE or OFFLOAD_CANCEL drains it; nfs4_free_cpntf_statelist then double-decrements and kfree's the still-linked object with no condition outside attacker control.\nPR:L - The attacker must be an established NFSv4.2 client of an export holding a valid open, lock, or delegation stateid to issue COPY_NOTIFY, which is authenticated low-privilege service access rather than a pre-authentication nfsd path.\nUI:N - No victim action is required; the attacking client drives COPY_NOTIFY, the concurrent READ that holds the cpntf reference, and CLOSE or OFFLOAD_CANCEL on its own NFS connections.\nS:U - The use-after-free corrupts kernel slab memory within the host nfsd security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - Use-after-free of struct nfs4_cpntf_state lets a concurrent find_cpntf_state reader dereference a kfree'd object; heap reuse of that slab gives the attacker control over freed contents, enabling arbitrary kernel memory disclosure.\nI:H - After the drain kfree, the holder still writes cpntf_time and later nfs4_put_cpntf_state runs _free_cpntf_state_locked on the freed object, a use-after-free write primitive usable for controlled memory modification and control-flow hijacking.\nA:H - The KASAN-detectable use-after-free at nfs4_put_cpntf_state oopses or panics nfsd worker threads, fully disrupting availability of the NFS server host."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T08:50:34.792Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.10.270"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.15.221"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.12.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}