{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-89708 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-89708 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-89708 and fix it if it is affected.\n\nWhat it is: CVE-2026-89708 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-89708 in the wild and no public exploit code.\n\nAffected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-89708/ (Markdown: https://insights.sbomify.com/CVE-2026-89708/index.md)","id":"CVE-2026-89708","markdown":"https://insights.sbomify.com/CVE-2026-89708/index.md","name":"CVE-2026-89708","record":{"aliases":["AZL-100118","BELL-CVE-2026-89708","DEBIAN-CVE-2026-89708","GHSA-m8hw-pq6j-j4w4","UBUNTU-CVE-2026-89708"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["code_execution","denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Linux kernel NFS","requires_auth":"none","summary":"A use-after-free vulnerability in the Linux kernel NFS server allows attackers to cause denial of service or potentially execute code during session teardown.","user_interaction":"not_required","vuln_class":"use_after_free"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":9.8,"severity":"critical","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[],"description":"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-\u003ecl_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 — 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) -\u003e kfree(ses)\n                                       nfsd4_cb_sequence_done()\n                                         reads cb_clp-\u003ecl_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-\u003ecl_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.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown","id":"CVE-2026-89708","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"use_after_free","year":"2026"},"n_packages":0,"n_references":4,"next":{"headline":"lockd, nfsd: RCU-protect nlmsvc_ops dispatch","id":"CVE-2026-89709"},"packages":[],"prev":{"headline":"nfsd: release path refs on follow_down() error","id":"CVE-2026-89707"},"products":["Linux"],"published":"2026-09-11","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"none","technical_impact":"total"},"state":"PUBLISHED","updated":"2026-10-19","vendors":["Linux"]},"summary":"A use-after-free vulnerability in the Linux kernel NFS server allows attackers to cause denial of service or potentially execute code during session teardown.","url":"https://insights.sbomify.com/CVE-2026-89708/"}