{"api_version":"1","generated_at":"2026-10-01T15:32:13+00:00","cve":"CVE-2026-97478","urls":{"html":"https://cve.report/CVE-2026-97478","api":"https://cve.report/api/cve/CVE-2026-97478.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-97478","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-97478"},"summary":{"title":"virt: acrn: Fix irqfd use-after-free during eventfd shutdown","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nvirt: acrn: Fix irqfd use-after-free during eventfd shutdown\n\nacrn_irqfd_deassign() and the eventfd EPOLLHUP wakeup can race and free\nthe same struct hsm_irqfd:\n\n  CPU0                                 CPU1\n  ----                                 ----\n  eventfd_release()\n    wake_up_poll(EPOLLHUP)\n      hsm_irqfd_wakeup()\n        queue_work(&irqfd->shutdown)\n                                       acrn_irqfd_deassign()\n                                         hsm_irqfd_shutdown()\n                                           list_del_init()\n                                           eventfd_ctx_remove_wait_queue()\n                                           eventfd_ctx_put()\n                                         kfree(irqfd)\n  hsm_irqfd_shutdown_work()\n    container_of(work, ..., shutdown)\n    irqfd->vm                  <-- use-after-free\n\nThe deassign path freed the irqfd while a shutdown work item was\nalready queued by EPOLLHUP (or vice versa), so the work item could\nresurrect a dangling pointer through container_of().\n\nSwitch to the lifetime model used by KVM irqfds:\n\n - Deassign/deinit only deactivate the irqfd: remove it from vm->irqfds\n   under irqfds_lock and queue the cleanup work.\n - hsm_irqfd_shutdown_work() becomes the sole owner that unhooks the\n   eventfd waitqueue entry, drops the eventfd reference and frees the\n   irqfd.\n - A new HSM_IRQFD_FLAG_SHUTDOWN bit guarded by test_and_set_bit()\n   ensures the cleanup work is queued at most once, no matter how many\n   of {EPOLLHUP, deassign, deinit} fire concurrently.  This is safe to\n   call from the waitqueue callback, which runs with wqh->lock held and\n   IRQs disabled and therefore cannot take irqfds_lock.\n - acrn_irqfd_deassign() flushes vm->irqfd_wq before returning so the\n   eventfd is fully detached on return.  acrn_irqfd_deinit() deactivates\n   every irqfd, flushes the workqueue and only then destroys it, so no\n   path can queue_work() onto a torn-down workqueue.\n - acrn_irqfd_assign() now installs the eventfd waitqueue entry and\n   publishes the irqfd to vm->irqfds under irqfds_lock, so the irqfd is\n   never visible to deassign/deinit before its waitqueue entry is in\n   place, and any EPOLLHUP that fires in the assign window queues\n   cleanup work that blocks on irqfds_lock until publication is done.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-24 17:17:25","updated_at":"2026-09-28 06:16:33"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/d8156aacfcabb81f52c20ef89094945434d08079","name":"https://git.kernel.org/stable/c/d8156aacfcabb81f52c20ef89094945434d08079","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/666c7f9e07925aa0863348f960e09bb89f8f05a3","name":"https://git.kernel.org/stable/c/666c7f9e07925aa0863348f960e09bb89f8f05a3","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-97478","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97478","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected aa3b483ff1d71c50b33db154048dff9a8f08ac71 d8156aacfcabb81f52c20ef89094945434d08079 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected aa3b483ff1d71c50b33db154048dff9a8f08ac71 666c7f9e07925aa0863348f960e09bb89f8f05a3 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.12","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.12 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.53 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"97478","cve":"CVE-2026-97478","epss":"0.001200000","percentile":"0.016480000","score_date":"2026-09-29","updated_at":"2026-09-30 00:11:23"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/virt/acrn/irqfd.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"d8156aacfcabb81f52c20ef89094945434d08079","status":"affected","version":"aa3b483ff1d71c50b33db154048dff9a8f08ac71","versionType":"git"},{"lessThan":"666c7f9e07925aa0863348f960e09bb89f8f05a3","status":"affected","version":"aa3b483ff1d71c50b33db154048dff9a8f08ac71","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/virt/acrn/irqfd.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.12"},{"lessThan":"5.12","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.53","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.53","versionStartIncluding":"5.12","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2","versionStartIncluding":"5.12","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvirt: acrn: Fix irqfd use-after-free during eventfd shutdown\n\nacrn_irqfd_deassign() and the eventfd EPOLLHUP wakeup can race and free\nthe same struct hsm_irqfd:\n\n  CPU0                                 CPU1\n  ----                                 ----\n  eventfd_release()\n    wake_up_poll(EPOLLHUP)\n      hsm_irqfd_wakeup()\n        queue_work(&irqfd->shutdown)\n                                       acrn_irqfd_deassign()\n                                         hsm_irqfd_shutdown()\n                                           list_del_init()\n                                           eventfd_ctx_remove_wait_queue()\n                                           eventfd_ctx_put()\n                                         kfree(irqfd)\n  hsm_irqfd_shutdown_work()\n    container_of(work, ..., shutdown)\n    irqfd->vm                  <-- use-after-free\n\nThe deassign path freed the irqfd while a shutdown work item was\nalready queued by EPOLLHUP (or vice versa), so the work item could\nresurrect a dangling pointer through container_of().\n\nSwitch to the lifetime model used by KVM irqfds:\n\n - Deassign/deinit only deactivate the irqfd: remove it from vm->irqfds\n   under irqfds_lock and queue the cleanup work.\n - hsm_irqfd_shutdown_work() becomes the sole owner that unhooks the\n   eventfd waitqueue entry, drops the eventfd reference and frees the\n   irqfd.\n - A new HSM_IRQFD_FLAG_SHUTDOWN bit guarded by test_and_set_bit()\n   ensures the cleanup work is queued at most once, no matter how many\n   of {EPOLLHUP, deassign, deinit} fire concurrently.  This is safe to\n   call from the waitqueue callback, which runs with wqh->lock held and\n   IRQs disabled and therefore cannot take irqfds_lock.\n - acrn_irqfd_deassign() flushes vm->irqfd_wq before returning so the\n   eventfd is fully detached on return.  acrn_irqfd_deinit() deactivates\n   every irqfd, flushes the workqueue and only then destroys it, so no\n   path can queue_work() onto a torn-down workqueue.\n - acrn_irqfd_assign() now installs the eventfd waitqueue entry and\n   publishes the irqfd to vm->irqfds under irqfds_lock, so the irqfd is\n   never visible to deassign/deinit before its waitqueue entry is in\n   place, and any EPOLLHUP that fires in the assign window queues\n   cleanup work that blocks on irqfds_lock until publication is done."}],"metrics":[{"cvssV3_1":{"baseScore":7.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:L - The UAF is reached from ioctl(ACRN_IOCTL_IRQFD) on /dev/acrn_hsm: acrn_dev_ioctl() copy_from_user()s struct acrn_irqfd and calls acrn_irqfd_config() → acrn_irqfd_assign()/acrn_irqfd_deassign(), while close() of that eventfd hits eventfd_release() → hsm_irqfd_wakeup(). No remote protocol carries the fd, flags, or EPOLLHUP.\nAC:L - The attacker owns both sides: one thread ioctl(ACRN_IOCTL_IRQFD) with ACRN_IRQFD_FLAG_DEASSIGN so acrn_irqfd_deassign() → hsm_irqfd_shutdown() kfree()s the hsm_irqfd, while another close()s a dup of the same eventfd so eventfd_release() → wake_up_poll(EPOLLHUP) → hsm_irqfd_wakeup() queues hsm_irqfd_shutdown_work(); the window is retryable.\nPR:L - acrn_dev_open(), acrn_dev_ioctl() and acrn_irqfd_config() have no capable()/CAP_* gate; only /dev/acrn_hsm DAC applies. ACRN Service VM deployments grant that node to the deprivileged acrn-dm device-model account (as with /dev/kvm), so a local user with that fd can CREATE_VM and IRQFD without init-namespace root.\nUI:N - The attacker opens /dev/acrn_hsm, ioctl(ACRN_IOCTL_CREATE_VM) then ACRN_IOCTL_IRQFD assign, and races close() of its own eventfd against deassign (or acrn_dev_release() → acrn_irqfd_deinit()); no other user must mount, open, or click.\nS:U - hsm_irqfd_shutdown_work() uses the freed struct hsm_irqfd in the Service VM kernel that runs acrn_dev_ioctl(). The attacker is already a Service VM process issuing HSM ioctls, not a User VM guest crossing into the ACRN hypervisor, so impact stays in one kernel authority.\nC:H - After acrn_irqfd_deassign() kfree()s the hsm_irqfd, hsm_irqfd_shutdown_work() container_of()s the queued work_struct and reads irqfd->vm (and later irqfd->eventfd) from the freed kmalloc object. Reclaiming that slot lets the attacker disclose reallocated kernel heap through those dangling loads.\nI:H - The same UAF lets hsm_irqfd_shutdown_work() mutex_lock(&irqfd->vm->irqfds_lock), list_del_init(&irqfd->list) and eventfd_ctx_put(irqfd->eventfd) on attacker-reclaimed hsm_irqfd fields, which is an arbitrary write / wait-queue function-pointer hijack, plus a second kfree of the sprayed object.\nA:H - hsm_irqfd_shutdown_work() loading irqfd->vm after hsm_irqfd_shutdown() kfree()s it oopses on a dangling pointer or corrupts the irqfds mutex/list; the EPOLLHUP work versus deassign kfree race in the commit is a Service VM kernel panic even without a successful spray."}]}],"providerMetadata":{"dateUpdated":"2026-09-28T05:30:07.313Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/d8156aacfcabb81f52c20ef89094945434d08079"},{"url":"https://git.kernel.org/stable/c/666c7f9e07925aa0863348f960e09bb89f8f05a3"}],"title":"virt: acrn: Fix irqfd use-after-free during eventfd shutdown","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-97478","datePublished":"2026-09-24T16:04:20.263Z","dateReserved":"2026-09-24T16:01:01.149Z","dateUpdated":"2026-09-28T05:30:07.313Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-24 17:17:25","lastModifiedDate":"2026-09-28 06:16:33","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"97478","Ordinal":"1","Title":"virt: acrn: Fix irqfd use-after-free during eventfd shutdown","CVE":"CVE-2026-97478","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"97478","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nvirt: acrn: Fix irqfd use-after-free during eventfd shutdown\n\nacrn_irqfd_deassign() and the eventfd EPOLLHUP wakeup can race and free\nthe same struct hsm_irqfd:\n\n  CPU0                                 CPU1\n  ----                                 ----\n  eventfd_release()\n    wake_up_poll(EPOLLHUP)\n      hsm_irqfd_wakeup()\n        queue_work(&irqfd->shutdown)\n                                       acrn_irqfd_deassign()\n                                         hsm_irqfd_shutdown()\n                                           list_del_init()\n                                           eventfd_ctx_remove_wait_queue()\n                                           eventfd_ctx_put()\n                                         kfree(irqfd)\n  hsm_irqfd_shutdown_work()\n    container_of(work, ..., shutdown)\n    irqfd->vm                  <-- use-after-free\n\nThe deassign path freed the irqfd while a shutdown work item was\nalready queued by EPOLLHUP (or vice versa), so the work item could\nresurrect a dangling pointer through container_of().\n\nSwitch to the lifetime model used by KVM irqfds:\n\n - Deassign/deinit only deactivate the irqfd: remove it from vm->irqfds\n   under irqfds_lock and queue the cleanup work.\n - hsm_irqfd_shutdown_work() becomes the sole owner that unhooks the\n   eventfd waitqueue entry, drops the eventfd reference and frees the\n   irqfd.\n - A new HSM_IRQFD_FLAG_SHUTDOWN bit guarded by test_and_set_bit()\n   ensures the cleanup work is queued at most once, no matter how many\n   of {EPOLLHUP, deassign, deinit} fire concurrently.  This is safe to\n   call from the waitqueue callback, which runs with wqh->lock held and\n   IRQs disabled and therefore cannot take irqfds_lock.\n - acrn_irqfd_deassign() flushes vm->irqfd_wq before returning so the\n   eventfd is fully detached on return.  acrn_irqfd_deinit() deactivates\n   every irqfd, flushes the workqueue and only then destroys it, so no\n   path can queue_work() onto a torn-down workqueue.\n - acrn_irqfd_assign() now installs the eventfd waitqueue entry and\n   publishes the irqfd to vm->irqfds under irqfds_lock, so the irqfd is\n   never visible to deassign/deinit before its waitqueue entry is in\n   place, and any EPOLLHUP that fires in the assign window queues\n   cleanup work that blocks on irqfds_lock until publication is done.","Type":"Description","Title":"virt: acrn: Fix irqfd use-after-free during eventfd shutdown"}]}}}