From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98264][MODERATE 7.0] ALSA: virtio: reset device before deleting virtqueues Date: Sat, 10 Oct 2026 15:38:39 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98264 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 8edc3669e3e22f0123a1114c3a03df9abc4cd465 List-Id: CVE: CVE-2026-98264 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: ALSA: virtio: reset device before deleting virtqueues Commit: 8edc3669e3e22f0123a1114c3a03df9abc4cd465 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8edc3669e3e22f0123a1114c3a03df9abc4cd465 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98264 Analysis date: Sat, 10 Oct 2026 15:38:39 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate Manual review required: NO Summary: ALSA virtio-sound can free vring backing while the device remains active, allowing post-free device access that may corrupt guest-kernel memory or crash the guest. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98264 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98264 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: MODERATE 7.0 Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98264 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98264 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF (independent Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'ALSA virtio sound can release vring backing memory while the virtio device still has enabled queues because del_vqs does not guarantee that the device is quiesced. The device may continue DMA access after the vring memory is freed, creating a use-after-free condition that can crash the guest kernel or corrupt memory if the released pages are reused. For the CVSS the PR:N value is used in the paranoid score because a malicious or faulty virtio backend can control queue activity without an account or privileges inside the guest. The attack is adjacent to the guest through the virtio device boundary and is not directly network reachable. Impact is at least denial of service and may include confidentiality and integrity impact because DMA can access freed and potentially reallocated kernel memory. This risk is most relevant for untrusted backends, isolated device processes, passthrough devices, or confidential guest threat models.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 4) MAYBE VIRT SIMPLEFIX HARDWARE LINUS INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO ## 1. ActionableScore * Raw conservative score: 3 * Conservative score: 3 * Raw paranoid score: 5 * Paranoid score: 5 * No floor or cap was applied. * Final recommended bucket: **Actionable Moderate**:: ## 2. Signal breakdown Conservative signals: * +2 Real UAF or lifetime violation. `del_vqs()` releases the vring backing while modern virtio-pci may leave the queue active, allowing device access after the backing memory lifetime ends. * +1 Constrained post-free DMA write. A virtio device can write used-ring or queue state to the fixed stale vring address. The destination and contents are not shown to be attacker-selectable. * Total: 3. Additional paranoid signals: * +1 Firmware or device-mediated influence. A faulty or malicious virtio backend can keep the queue active and issue accesses during teardown. * +1 Realistic kernel crash or strong DoS. DMA into freed and potentially reused guest-kernel memory can plausibly corrupt state and crash the guest. * Total: 5. Not awarded: * No strong corruption +2 because controlled reclaim, attacker-selected destination, attacker-controlled payload, or directed write is not established. * No structured stale-object leverage because this is fixed stale vring storage rather than demonstrated attacker-shaped replacement of an active structured object. * No attacker-influenced lifetime bonus because the same below-host-admin principal is not shown to control both teardown and the relevant device access. * No confidentiality or integrity bonus because no protected replacement object, disclosure path, or unauthorized persistent state modification is identified. * No extra Availability point because no persistent effect distinct from the possible crash is established. * No direct remote-reachability bonus. Access is mediated by a virtio device or backend, not network traffic. * No hard-race penalty. The ordering is wrong by construction, but the supplied evidence does not establish that the access window is exceptionally narrow or impractical. * B5-R is not established. There is no retry-accumulated index or offset. * B3-PENDING is not established. The stale vring is not demonstrated to be shared or file-backed storage crossing an ownership boundary. * B4-PENDING is not applicable because no authorization decision is involved. No concrete repeated release or refcount operation exists: * The first operation frees vring backing through `del_vqs()`. * No exact reference is shown reaching a second `put`, `free`, or refcount mutation. * The later operation is asynchronous device access, not a second lifetime release. * Concrete repeated release bonus: not awarded. * Paranoid repeated-refcount bonus: not awarded. * FLOOR 5 for repeated release: not applied. ## 3. Reachability analysis The vulnerable transitions occur in `virtsnd_remove()`, `virtsnd_freeze()`, and probe-failure unwind after `DRIVER_OK`. A guest-local actor initiating device removal, suspend, or freeze may require administrative device-management privileges. The patch does not establish the exact guest-side privilege checks. Conversely, a faulty or malicious virtio backend may influence queue activity or probe behavior without a user account inside the guest. The complete trigger for either attacker model is not sufficiently shown, so `HostAdminRequired=UNKNOWN`. No namespace-scoped capability path is established. No prior network configuration or direct remote packet trigger exists. The relevant prerequisite is a virtio-sound device using queue semantics where `del_vqs()` does not quiesce the device. This is virtualization-specific but is not proven to require rare physical hardware. The vulnerable ordering is deterministic. Actual post-free access depends on pending or concurrent device activity, but the evidence does not prove an unusually hard one-shot race. ## 4. Primitive and severity interpretation The exact primitive is asynchronous device access to freed vring backing memory. This is a real DMA-equivalent lifetime violation and therefore CLASS_B. The stale object is best classified as fixed stale storage. The old queue address remains available to the device after software frees its backing. There is no demonstrated controlled replacement, reclaim strategy, callback consumption, arbitrary target selection, or repeated refcount mutation. The demonstrated mechanics support possible writes to memory outside its original lifetime. The practical consequence is guest-kernel memory corruption or a guest crash. Stronger consequences such as controlled corruption, information disclosure, or guest privilege escalation remain speculative. `ImportantCandidate=NO` because the supplied evidence does not establish meaningful exploitation leverage beyond a constrained fixed-address post-free device access. `AutoDowngradeAllowed=YES` because no controlled reclaim, security-boundary bypass, repeated lifetime mutation, or independently useful corruption primitive remains unresolved. The paranoid score nevertheless keeps the issue actionable due to the concrete UAF and plausible crash. ## 5. One-sentence report phrase ALSA virtio-sound can free vring backing while the device remains active, allowing post-free device access that may corrupt guest-kernel memory or crash the guest. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Confirm whether the affected backend can write after `del_vqs()`, whether freed vring pages can be reused before reset, and whether an attacker below host-admin privilege can induce the complete freeze, removal, or probe-failure sequence. ## 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ALSA: virtio: reset device before deleting virtqueues Commit: 8edc3669e3e22f0123a1114c3a03df9abc4cd465 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8edc3669e3e22f0123a1114c3a03df9abc4cd465 Commit description: virtsnd_remove() and virtsnd_freeze() delete the virtqueues before resetting the device. del_vqs() frees the vring backing, but does not provide a generic device quiesce operation. In particular, modern virtio-pci keeps enabled queues active until the device is reset. Reset the device before deleting the virtqueues so it can no longer access the vring memory when that memory is released. This also covers probe failures after DRIVER_OK, which unwind through virtsnd_remove(). Fixes: de3a998 ("ALSA: virtio: add virtio sound driver") Fixes: 575483e ("ALSA: virtio: introduce device suspend/resume support") Cc: stable@vger.kernel.org Signed-off-by: Yuho Choi Link: https://patch.msgid.link/20260911031121.1542502-1-oss.patchbox@gmail.com Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman Changed files: sound/virtio/virtio_card.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8edc3669e3e22f0123a1114c3a03df9abc4cd465 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98264 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98264 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.5 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: 3 Paranoid ActionableScore: 5 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE 7.0 These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).