{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-89708", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.751Z", "datePublished": "2026-09-11T19:46:24.061Z", "dateUpdated": "2026-10-19T08:51:21.242Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:21.242Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown\n\nAfter a DESTROY_SESSION the per-session teardown path can free a\nsession while rpciod still holds an inflight callback rpc_task that\ndereferences clp->cl_cb_session. nfsd4_probe_callback_sync() flushes\ncl_callback_wq, but once nfsd4_run_cb_work() has called\nrpc_call_async() the rpc_task lives on rpciod; flushing the workqueue\ndoes not wait for it. rpc_shutdown_client() does drain rpciod tasks,\nbut uses a 1-second wait_event_timeout \u2014 tasks stuck in rpc_delay()\n(e.g. 2-second NFS4ERR_DELAY retries) can outlive the drain.\n\n destroy path rpciod\n ------------ ------\n unhash_session(ses)\n nfsd4_probe_callback_sync(clp)\n flush_workqueue(cl_callback_wq)\n /* returns; rpc_task still live */\n nfsd4_put_session_locked(ses)\n free_session(ses) -> kfree(ses)\n nfsd4_cb_sequence_done()\n reads cb_clp->cl_cb_session\n /* freed slab */\n\nA second window exists in nfsd4_process_cb_update(). When\n__nfsd4_find_backchannel() returns NULL because unhash_session() has\nalready removed the destroyed session from cl_sessions,\nsetup_callback_client() takes the v4.1 early return so\nclp->cl_cb_session = ses never fires and the field retains a pointer\nto the about-to-be-freed session.\n\nFix both by converting cl_cb_session to an RCU-protected pointer:\n\n - Move the cl_cb_session = ses assignment in setup_callback_client()\n to after rpc_create() succeeds, so it is only published when a\n working backchannel exists. Clear cl_cb_session on the error\n return in nfsd4_process_cb_update(). Both stores use\n rcu_assign_pointer().\n\n - Annotate cl_cb_session with __rcu. All rpciod-side readers use\n rcu_read_lock()/rcu_dereference() and check for NULL, bailing to\n the appropriate error or requeue path:\n encode_cb_sequence4args(), decode_cb_sequence4resok(),\n nfsd41_cb_get_slot(), nfsd41_cb_release_slot(),\n nfsd4_cb_prepare(), and nfsd4_cb_sequence_done().\n\n - Switch __free_session() from kfree() to kfree_rcu() so the\n session slab is not reclaimed until after an RCU grace period,\n guaranteeing that rpciod readers inside rcu_read_lock() never\n dereference freed memory.\n\n - Pass the session pointer to the nfsd_cb_seq_status and\n nfsd_cb_free_slot tracepoints instead of having them re-read\n cl_cb_session.\n\n - nfsd4_cb_prepare() calls rpc_exit() when the session is NULL,\n routing through the done/release path to requeue the callback."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL"}, "scenarios": [{"lang": "en", "value": "AV:N - The UAF is in nfsd NFSv4.1 session teardown (nfsd4_destroy_session) and the rpciod callback path (nfsd4_cb_sequence_done). DESTROY_SESSION and the inflight CB_COMPOUND run over TCP/2049, so a remote NFS client reaches the bug with no local access.\nAC:L - The attacker controls both sides: they keep a callback rpc_task on rpciod (e.g. NFS4ERR_DELAY so rpc_delay is 2s) and send DESTROY_SESSION. flush_workqueue does not wait for rpciod, and rpc_shutdown_client's 1s drain can expire first, so the window is attacker-driven and retryable.\nPR:N - Typical nfsd exports use AUTH_SYS/AUTH_NULL, so RPC identities are self-asserted. EXCHANGE_ID, CREATE_SESSION with a backchannel, OPEN, and DESTROY_SESSION succeed for any host allowed by the export; nfsd4_mach_creds_match is a no-op under default SP4_NONE. No local account is required.\nUI:N - The attacking NFS client issues CREATE_SESSION, OPEN/CB_RECALL traffic, NFS4ERR_DELAY replies, and DESTROY_SESSION itself. No victim on the server must mount a filesystem, open a file, or take any other action.\nS:U - The use-after-free corrupts a kmalloc'd nfsd4_session in the host nfsd kernel. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After free_session kfree's the session, rpciod still reads se_sessionid and se_cb_seq_nr in encode_cb_sequence4args and decode_cb_sequence4resok. Reclaim of that slab lets the attacker disclose kernel memory via the callback they receive. Per kernel guidance a UAF is C:H.\nI:H - The same dangling cl_cb_session is written by update_cb_slot_table (attacker-controlled target_highest_slotid), grab_slot/nfsd41_cb_release_slot (se_cb_slot_avail and se_lock), and nfsd4_cb_sequence_done (se_cb_seq_nr++). That is a UAF write primitive for heap corruption and control-flow hijack.\nA:H - Use-after-free of struct nfsd4_session from an rpciod callback oopses or panics the NFS server even without full exploitation, and the attacker can repeat DESTROY_SESSION against inflight callbacks to deny service."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/nfsd/nfs4callback.c", "fs/nfsd/nfs4state.c", "fs/nfsd/state.h", "fs/nfsd/trace.h"], "versions": [{"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "2775ec1d617e665eab71ce0f13ab1f7959713a2b", "status": "affected", "versionType": "git"}, {"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "f164eb52b6f3cbf40f07fe379f9f421f88e02f76", "status": "affected", "versionType": "git"}, {"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25", "status": "affected", "versionType": "git"}, {"version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "01c5d5f58a5db9b0ee5afba2e49d3157788687b2", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/nfsd/nfs4callback.c", "fs/nfsd/nfs4state.c", "fs/nfsd/state.h", "fs/nfsd/trace.h"], "versions": [{"version": "2.6.38", "status": "affected"}, {"version": "0", "lessThan": "2.6.38", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.111", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "6.12.111"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "6.18.50"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "7.2.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.38", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/2775ec1d617e665eab71ce0f13ab1f7959713a2b"}, {"url": "https://git.kernel.org/stable/c/f164eb52b6f3cbf40f07fe379f9f421f88e02f76"}, {"url": "https://git.kernel.org/stable/c/13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25"}, {"url": "https://git.kernel.org/stable/c/01c5d5f58a5db9b0ee5afba2e49d3157788687b2"}], "title": "nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-89708", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T19:26:20.755207Z"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:49.405Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-89708", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T19:26:20.755207Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:21.286Z"}}], "cna": {"title": "nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown", "metrics": [{"cvssV3_1": {"version": "3.1", "baseScore": 9.8, "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}, "scenarios": [{"lang": "en", "value": "AV:N - The UAF is in nfsd NFSv4.1 session teardown (nfsd4_destroy_session) and the rpciod callback path (nfsd4_cb_sequence_done). DESTROY_SESSION and the inflight CB_COMPOUND run over TCP/2049, so a remote NFS client reaches the bug with no local access.\nAC:L - The attacker controls both sides: they keep a callback rpc_task on rpciod (e.g. NFS4ERR_DELAY so rpc_delay is 2s) and send DESTROY_SESSION. flush_workqueue does not wait for rpciod, and rpc_shutdown_client's 1s drain can expire first, so the window is attacker-driven and retryable.\nPR:N - Typical nfsd exports use AUTH_SYS/AUTH_NULL, so RPC identities are self-asserted. EXCHANGE_ID, CREATE_SESSION with a backchannel, OPEN, and DESTROY_SESSION succeed for any host allowed by the export; nfsd4_mach_creds_match is a no-op under default SP4_NONE. No local account is required.\nUI:N - The attacking NFS client issues CREATE_SESSION, OPEN/CB_RECALL traffic, NFS4ERR_DELAY replies, and DESTROY_SESSION itself. No victim on the server must mount a filesystem, open a file, or take any other action.\nS:U - The use-after-free corrupts a kmalloc'd nfsd4_session in the host nfsd kernel. Impact stays in that kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After free_session kfree's the session, rpciod still reads se_sessionid and se_cb_seq_nr in encode_cb_sequence4args and decode_cb_sequence4resok. Reclaim of that slab lets the attacker disclose kernel memory via the callback they receive. Per kernel guidance a UAF is C:H.\nI:H - The same dangling cl_cb_session is written by update_cb_slot_table (attacker-controlled target_highest_slotid), grab_slot/nfsd41_cb_release_slot (se_cb_slot_avail and se_lock), and nfsd4_cb_sequence_done (se_cb_seq_nr++). That is a UAF write primitive for heap corruption and control-flow hijack.\nA:H - Use-after-free of struct nfsd4_session from an rpciod callback oopses or panics the NFS server even without full exploitation, and the attacker can repeat DESTROY_SESSION against inflight callbacks to deny service."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "2775ec1d617e665eab71ce0f13ab1f7959713a2b", "versionType": "git"}, {"status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "f164eb52b6f3cbf40f07fe379f9f421f88e02f76", "versionType": "git"}, {"status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25", "versionType": "git"}, {"status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "lessThan": "01c5d5f58a5db9b0ee5afba2e49d3157788687b2", "versionType": "git"}], "programFiles": ["fs/nfsd/nfs4callback.c", "fs/nfsd/nfs4state.c", "fs/nfsd/state.h", "fs/nfsd/trace.h"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "2.6.38"}, {"status": "unaffected", "version": "0", "lessThan": "2.6.38", "versionType": "semver"}, {"status": "unaffected", "version": "6.12.111", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.18.50", "versionType": "semver", "lessThanOrEqual": "6.18.*"}, {"status": "unaffected", "version": "7.2.4", "versionType": "semver", "lessThanOrEqual": "7.2.*"}, {"status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["fs/nfsd/nfs4callback.c", "fs/nfsd/nfs4state.c", "fs/nfsd/state.h", "fs/nfsd/trace.h"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/2775ec1d617e665eab71ce0f13ab1f7959713a2b"}, {"url": "https://git.kernel.org/stable/c/f164eb52b6f3cbf40f07fe379f9f421f88e02f76"}, {"url": "https://git.kernel.org/stable/c/13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25"}, {"url": "https://git.kernel.org/stable/c/01c5d5f58a5db9b0ee5afba2e49d3157788687b2"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown\n\nAfter a DESTROY_SESSION the per-session teardown path can free a\nsession while rpciod still holds an inflight callback rpc_task that\ndereferences clp->cl_cb_session. nfsd4_probe_callback_sync() flushes\ncl_callback_wq, but once nfsd4_run_cb_work() has called\nrpc_call_async() the rpc_task lives on rpciod; flushing the workqueue\ndoes not wait for it. rpc_shutdown_client() does drain rpciod tasks,\nbut uses a 1-second wait_event_timeout \u2014 tasks stuck in rpc_delay()\n(e.g. 2-second NFS4ERR_DELAY retries) can outlive the drain.\n\n destroy path rpciod\n ------------ ------\n unhash_session(ses)\n nfsd4_probe_callback_sync(clp)\n flush_workqueue(cl_callback_wq)\n /* returns; rpc_task still live */\n nfsd4_put_session_locked(ses)\n free_session(ses) -> kfree(ses)\n nfsd4_cb_sequence_done()\n reads cb_clp->cl_cb_session\n /* freed slab */\n\nA second window exists in nfsd4_process_cb_update(). When\n__nfsd4_find_backchannel() returns NULL because unhash_session() has\nalready removed the destroyed session from cl_sessions,\nsetup_callback_client() takes the v4.1 early return so\nclp->cl_cb_session = ses never fires and the field retains a pointer\nto the about-to-be-freed session.\n\nFix both by converting cl_cb_session to an RCU-protected pointer:\n\n - Move the cl_cb_session = ses assignment in setup_callback_client()\n to after rpc_create() succeeds, so it is only published when a\n working backchannel exists. Clear cl_cb_session on the error\n return in nfsd4_process_cb_update(). Both stores use\n rcu_assign_pointer().\n\n - Annotate cl_cb_session with __rcu. All rpciod-side readers use\n rcu_read_lock()/rcu_dereference() and check for NULL, bailing to\n the appropriate error or requeue path:\n encode_cb_sequence4args(), decode_cb_sequence4resok(),\n nfsd41_cb_get_slot(), nfsd41_cb_release_slot(),\n nfsd4_cb_prepare(), and nfsd4_cb_sequence_done().\n\n - Switch __free_session() from kfree() to kfree_rcu() so the\n session slab is not reclaimed until after an RCU grace period,\n guaranteeing that rpciod readers inside rcu_read_lock() never\n dereference freed memory.\n\n - Pass the session pointer to the nfsd_cb_seq_status and\n nfsd_cb_free_slot tracepoints instead of having them re-read\n cl_cb_session.\n\n - nfsd4_cb_prepare() calls rpc_exit() when the session is NULL,\n routing through the done/release path to requeue the callback."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.111", "versionStartIncluding": "2.6.38"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.50", "versionStartIncluding": "2.6.38"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.2.4", "versionStartIncluding": "2.6.38"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.3", "versionStartIncluding": "2.6.38"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:21.242Z"}}}, "cveMetadata": {"cveId": "CVE-2026-89708", "state": "PUBLISHED", "dateUpdated": "2026-10-19T08:51:21.242Z", "dateReserved": "2026-09-11T19:38:34.751Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-09-11T19:46:24.061Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/nfsd/nfs4callback.c", "fs/nfsd/nfs4state.c", "fs/nfsd/state.h", "fs/nfsd/trace.h"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "2775ec1d617e665eab71ce0f13ab1f7959713a2b", "status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "versionType": "git"}, {"lessThan": "f164eb52b6f3cbf40f07fe379f9f421f88e02f76", "status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "versionType": "git"}, {"lessThan": "13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25", "status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "versionType": "git"}, {"lessThan": "01c5d5f58a5db9b0ee5afba2e49d3157788687b2", "status": "affected", "version": "dcbeaa68dbbdacbbb330a86c7fc95a28473fc209", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/nfsd/nfs4callback.c", "fs/nfsd/nfs4state.c", "fs/nfsd/state.h", "fs/nfsd/trace.h"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "2.6.38"}, {"lessThan": "2.6.38", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.111", "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", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown\n\nAfter a DESTROY_SESSION the per-session teardown path can free a\nsession while rpciod still holds an inflight callback rpc_task that\ndereferences clp->cl_cb_session. nfsd4_probe_callback_sync() flushes\ncl_callback_wq, but once nfsd4_run_cb_work() has called\nrpc_call_async() the rpc_task lives on rpciod; flushing the workqueue\ndoes not wait for it. rpc_shutdown_client() does drain rpciod tasks,\nbut uses a 1-second wait_event_timeout \u2014 tasks stuck in rpc_delay()\n(e.g. 2-second NFS4ERR_DELAY retries) can outlive the drain.\n\n destroy path rpciod\n ------------ ------\n unhash_session(ses)\n nfsd4_probe_callback_sync(clp)\n flush_workqueue(cl_callback_wq)\n /* returns; rpc_task still live */\n nfsd4_put_session_locked(ses)\n free_session(ses) -> kfree(ses)\n nfsd4_cb_sequence_done()\n reads cb_clp->cl_cb_session\n /* freed slab */\n\nA second window exists in nfsd4_process_cb_update(). When\n__nfsd4_find_backchannel() returns NULL because unhash_session() has\nalready removed the destroyed session from cl_sessions,\nsetup_callback_client() takes the v4.1 early return so\nclp->cl_cb_session = ses never fires and the field retains a pointer\nto the about-to-be-freed session.\n\nFix both by converting cl_cb_session to an RCU-protected pointer:\n\n - Move the cl_cb_session = ses assignment in setup_callback_client()\n to after rpc_create() succeeds, so it is only published when a\n working backchannel exists. Clear cl_cb_session on the error\n return in nfsd4_process_cb_update(). Both stores use\n rcu_assign_pointer().\n\n - Annotate cl_cb_session with __rcu. All rpciod-side readers use\n rcu_read_lock()/rcu_dereference() and check for NULL, bailing to\n the appropriate error or requeue path:\n encode_cb_sequence4args(), decode_cb_sequence4resok(),\n nfsd41_cb_get_slot(), nfsd41_cb_release_slot(),\n nfsd4_cb_prepare(), and nfsd4_cb_sequence_done().\n\n - Switch __free_session() from kfree() to kfree_rcu() so the\n session slab is not reclaimed until after an RCU grace period,\n guaranteeing that rpciod readers inside rcu_read_lock() never\n dereference freed memory.\n\n - Pass the session pointer to the nfsd_cb_seq_status and\n nfsd_cb_free_slot tracepoints instead of having them re-read\n cl_cb_session.\n\n - nfsd4_cb_prepare() calls rpc_exit() when the session is NULL,\n routing through the done/release path to requeue the callback."}], "id": "CVE-2026-89708", "lastModified": "2026-10-19T09:18:09.590", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-89708", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T19:26:20.755207Z", "version": "2.0.3"}}]}, "published": "2026-09-11T20:19:58.140", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/01c5d5f58a5db9b0ee5afba2e49d3157788687b2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/2775ec1d617e665eab71ce0f13ab1f7959713a2b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f164eb52b6f3cbf40f07fe379f9f421f88e02f76"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: Linux kernel nfsd: Use-after-free during NFSv4 session teardown", "id": "2532446", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2532446"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-825", "details": ["A flaw was found in the Linux kernel's NFS daemon (nfsd). During the teardown of an NFSv4 session, a race condition can occur where the session's memory is freed while an active callback task still holds a reference to it. This can lead to a use-after-free vulnerability, potentially causing system instability, crashes, or denial of service."], "name": "CVE-2026-89708", "public_date": "2026-09-11T19:46:24Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-89708\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-89708\nhttps://git.kernel.org/stable/c/01c5d5f58a5db9b0ee5afba2e49d3157788687b2\nhttps://git.kernel.org/stable/c/13bdd486c3aad4fc19e6d8b9c3556a4b4c190b25\nhttps://git.kernel.org/stable/c/f164eb52b6f3cbf40f07fe379f9f421f88e02f76"], "threat_severity": "Important"}