{"api_version":"1","generated_at":"2026-09-12T13:54:27+00:00","cve":"CVE-2026-89689","urls":{"html":"https://cve.report/CVE-2026-89689","api":"https://cve.report/api/cve/CVE-2026-89689.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89689","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89689"},"summary":{"title":"nfsd: don't free session slots that are still in use","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: don't free session slots that are still in use\n\nnfsd4_sequence() can free the very slot it is currently processing.\nWhen the session shrinker has reduced se_target_maxslots below\nse_fchannel.maxreqs, the shrink path checks three conditions before\ncalling free_session_slots():\n\n  1. se_target_maxslots < maxreqs  (shrink was advertised)\n  2. slot->sl_generation == se_slot_gen  (slot is up-to-date)\n  3. seq->maxslots <= se_target_maxslots  (client acknowledges)\n\nHowever, seq->slotid is never checked against se_target_maxslots.\nA client using a slot in the range [se_target_maxslots, maxreqs) can\nsatisfy all three conditions: its slot has the current generation\n(set by a prior SEQUENCE), and it sends sa_highest_slotid <=\nse_target_maxslots to acknowledge the reduction.\n\nfree_session_slots() then kfrees every slot at index >=\nse_target_maxslots, including the caller's own slot. The function\ncontinues to write sl_seqid, sl_flags, sl_generation, and stores the\ndangling pointer in cstate->slot. Later, nfsd4_store_cache_entry()\ncopies up to maxresp_cached bytes of the compound reply into the freed\nsl_data[] array, corrupting whatever slab object now occupies that\naddress.\n\nAdditionally, a concurrent thread processing SEQUENCE on a different\nhigh-numbered slot can have its slot freed out from under it.\nNFSD4_SLOT_INUSE is set under nn->client_lock before the lock is\nreleased, so any concurrent thread past SEQUENCE will have its slot\nmarked. However, free_session_slots() does not check NFSD4_SLOT_INUSE\nbefore freeing.\n\nFix both problems by:\n 1. Checking that the current request's slotid is below the shrink\n    boundary.\n 2. Scanning slots in the to-be-freed range for NFSD4_SLOT_INUSE and\n    deferring the shrink if any are active.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-11 20:19:55","updated_at":"2026-09-11 20:19:55"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/72d40b103bb03f0124d3a3c8f71a30cbafaf6afa","name":"https://git.kernel.org/stable/c/72d40b103bb03f0124d3a3c8f71a30cbafaf6afa","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f5d22e372f4ac3eb287037a488c29691d52a6330","name":"https://git.kernel.org/stable/c/f5d22e372f4ac3eb287037a488c29691d52a6330","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b449b134e7762ddf98653a4b1d3e76d2d212ea64","name":"https://git.kernel.org/stable/c/b449b134e7762ddf98653a4b1d3e76d2d212ea64","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89689","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89689","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 72d40b103bb03f0124d3a3c8f71a30cbafaf6afa git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 b449b134e7762ddf98653a4b1d3e76d2d212ea64 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7 f5d22e372f4ac3eb287037a488c29691d52a6330 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.14","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.14 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.50 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.4 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["fs/nfsd/nfs4state.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"72d40b103bb03f0124d3a3c8f71a30cbafaf6afa","status":"affected","version":"fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7","versionType":"git"},{"lessThan":"b449b134e7762ddf98653a4b1d3e76d2d212ea64","status":"affected","version":"fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7","versionType":"git"},{"lessThan":"f5d22e372f4ac3eb287037a488c29691d52a6330","status":"affected","version":"fc8738c68d0bbf5033dd98b4f63d277ecbd49fd7","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["fs/nfsd/nfs4state.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.14"},{"lessThan":"6.14","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.50","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.4","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":"6.18.50","versionStartIncluding":"6.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.4","versionStartIncluding":"6.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"6.14","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: don't free session slots that are still in use\n\nnfsd4_sequence() can free the very slot it is currently processing.\nWhen the session shrinker has reduced se_target_maxslots below\nse_fchannel.maxreqs, the shrink path checks three conditions before\ncalling free_session_slots():\n\n  1. se_target_maxslots < maxreqs  (shrink was advertised)\n  2. slot->sl_generation == se_slot_gen  (slot is up-to-date)\n  3. seq->maxslots <= se_target_maxslots  (client acknowledges)\n\nHowever, seq->slotid is never checked against se_target_maxslots.\nA client using a slot in the range [se_target_maxslots, maxreqs) can\nsatisfy all three conditions: its slot has the current generation\n(set by a prior SEQUENCE), and it sends sa_highest_slotid <=\nse_target_maxslots to acknowledge the reduction.\n\nfree_session_slots() then kfrees every slot at index >=\nse_target_maxslots, including the caller's own slot. The function\ncontinues to write sl_seqid, sl_flags, sl_generation, and stores the\ndangling pointer in cstate->slot. Later, nfsd4_store_cache_entry()\ncopies up to maxresp_cached bytes of the compound reply into the freed\nsl_data[] array, corrupting whatever slab object now occupies that\naddress.\n\nAdditionally, a concurrent thread processing SEQUENCE on a different\nhigh-numbered slot can have its slot freed out from under it.\nNFSD4_SLOT_INUSE is set under nn->client_lock before the lock is\nreleased, so any concurrent thread past SEQUENCE will have its slot\nmarked. However, free_session_slots() does not check NFSD4_SLOT_INUSE\nbefore freeing.\n\nFix both problems by:\n 1. Checking that the current request's slotid is below the shrink\n    boundary.\n 2. Scanning slots in the to-be-freed range for NFSD4_SLOT_INUSE and\n    deferring the shrink if any are active."}],"providerMetadata":{"dateUpdated":"2026-09-11T19:46:09.976Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/72d40b103bb03f0124d3a3c8f71a30cbafaf6afa"},{"url":"https://git.kernel.org/stable/c/b449b134e7762ddf98653a4b1d3e76d2d212ea64"},{"url":"https://git.kernel.org/stable/c/f5d22e372f4ac3eb287037a488c29691d52a6330"}],"title":"nfsd: don't free session slots that are still in use","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89689","datePublished":"2026-09-11T19:46:09.976Z","dateReserved":"2026-09-11T19:38:34.749Z","dateUpdated":"2026-09-11T19:46:09.976Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-11 20:19:55","lastModifiedDate":"2026-09-11 20:19:55","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89689","Ordinal":"1","Title":"nfsd: don't free session slots that are still in use","CVE":"CVE-2026-89689","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89689","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: don't free session slots that are still in use\n\nnfsd4_sequence() can free the very slot it is currently processing.\nWhen the session shrinker has reduced se_target_maxslots below\nse_fchannel.maxreqs, the shrink path checks three conditions before\ncalling free_session_slots():\n\n  1. se_target_maxslots < maxreqs  (shrink was advertised)\n  2. slot->sl_generation == se_slot_gen  (slot is up-to-date)\n  3. seq->maxslots <= se_target_maxslots  (client acknowledges)\n\nHowever, seq->slotid is never checked against se_target_maxslots.\nA client using a slot in the range [se_target_maxslots, maxreqs) can\nsatisfy all three conditions: its slot has the current generation\n(set by a prior SEQUENCE), and it sends sa_highest_slotid <=\nse_target_maxslots to acknowledge the reduction.\n\nfree_session_slots() then kfrees every slot at index >=\nse_target_maxslots, including the caller's own slot. The function\ncontinues to write sl_seqid, sl_flags, sl_generation, and stores the\ndangling pointer in cstate->slot. Later, nfsd4_store_cache_entry()\ncopies up to maxresp_cached bytes of the compound reply into the freed\nsl_data[] array, corrupting whatever slab object now occupies that\naddress.\n\nAdditionally, a concurrent thread processing SEQUENCE on a different\nhigh-numbered slot can have its slot freed out from under it.\nNFSD4_SLOT_INUSE is set under nn->client_lock before the lock is\nreleased, so any concurrent thread past SEQUENCE will have its slot\nmarked. However, free_session_slots() does not check NFSD4_SLOT_INUSE\nbefore freeing.\n\nFix both problems by:\n 1. Checking that the current request's slotid is below the shrink\n    boundary.\n 2. Scanning slots in the to-be-freed range for NFSD4_SLOT_INUSE and\n    deferring the shrink if any are active.","Type":"Description","Title":"nfsd: don't free session slots that are still in use"}]}}}