From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98766][MODERATE 7.0] usb: gadget: aspeed-vhub: cancel wake work on device removal Date: Sat, 24 Oct 2026 08:35:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98766 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: f343bfa3fc9f6255602d66f4a7dbe7ddef13ba41 List-Id: CVE: CVE-2026-98766 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: usb: gadget: aspeed-vhub: cancel wake work on device removal Commit: f343bfa3fc9f6255602d66f4a7dbe7ddef13ba41 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f343bfa3fc9f6255602d66f4a7dbe7ddef13ba41 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98766 Analysis date: Sat, 24 Oct 2026 08:35:07 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: ASPEED vhub removal can race gadget wakeup and leave an embedded worker dereferencing devm-freed hub state, causing a teardown-time kernel UAF with plausible crash impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98766 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98766 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-2026-98766 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98766 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=5 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/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';DESCR 'A race between ASPEED virtual hub removal and the gadget wakeup callback can leave wake_work queued after devm has freed vhub and its downstream port objects. The delayed worker then dereferences stale kernel memory, giving a concrete use after free primitive with at least kernel crash impact and a plausible but unproven path to wider memory corruption after slab reuse. For the CVSS the PR:L value in the paranoid vector assumes that a delegated gadget management service or limited local component can coordinate device removal with wakeup activity. AC:H reflects the required timing window between clearing device state, cancelling work, and a concurrent wakeup request. This is not directly network reachable, and USB remote wakeup describes a USB bus operation rather than an Internet attack vector. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 1.9 and ActionableScore 5 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE USB INIT ERRORPATH UAF HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: -2 * Conservative score: 0; normalized to the scoring range minimum. * Raw paranoid score: -2 * Paranoid score: 0; no additional exploit leverage is evidence-supported. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +2 — Real UAF: queued `wake_work` can execute after devm has freed `vhub` and its ports. * +1 — Plausible kernel crash: the worker derives and dereferences the freed structured `vhub`. * -2 — Host-admin-equivalent trigger: maliciously invoking platform-device removal/unbind requires host device-management authority; delegated lower-privilege control is only hypothesized. * -1 — Hard one-shot teardown race: wakeup must re-arm or remain queued during the narrow removal/cancellation interval. * -2 — Rare hardware-only path: this requires the ASPEED virtual-hub controller and driver. Not awarded: controlled reclaim, attacker-shaped replacement contents, directed write, callback control, disclosure, C/I impact, or LPE. Generic slab reuse does not justify a paranoid point. No extra availability point duplicates the same crash. NEW52/B5-R and NEW53/B3-PENDING do not apply: there is no retry-accumulated OOB write or shared-backing write. 3. Reachability analysis The complete malicious trigger combines gadget wakeup activity with ASPEED platform-driver removal. The patch establishes the concurrency mechanics but not a below-host-admin interface capable of initiating removal. No namespace-scoped capability path is shown, and this platform device is not ordinarily instantiated by an attacker. Numeric host UID 0 is not strictly established because equivalent administrative capabilities may suffice. 4. Primitive and severity reading This is a real asynchronous UAF of an active structured object, not merely fixed stale transfer storage. The stale worker can consume `vhub` and port state after teardown. However, use is removal-only, attacker-controlled reclaim or post-free contents are absent, and no separate useful primitive past a likely fault is shown. It is therefore constrained CLASS_B, not CLASS_A. ImportantCandidate is NO and auto-downgrade remains allowed because the demonstrated path is host-admin-triggered, hardware-specific, race-dependent, and primarily crash-oriented. 5. One-sentence report phrase ASPEED vhub removal can race gadget wakeup and leave an embedded worker dereferencing devm-freed hub state, causing a teardown-time kernel UAF with plausible crash impact. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm whether any deployed gadget-management service can trigger both removal and wakeup below host-admin authority. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: usb: gadget: aspeed-vhub: cancel wake work on device removal Commit: f343bfa3fc9f6255602d66f4a7dbe7ddef13ba41 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f343bfa3fc9f6255602d66f4a7dbe7ddef13ba41 Commit description: wake_work is armed from the gadget .wakeup callback to resume suspended downstream ports, and it is never cancelled in ast_vhub_remove(), so a work item queued before or during removal can run after devm has freed vhub and its ports, a use-after-free. Cancelling the work alone is not sufficient: usb_gadget_wakeup() takes no lock and the unbind path never clears wakeup_en, so a remote-wakeup request in flight on another CPU can re-arm the work after the cancel and before vhub is freed. ast_vhub_del_dev() already clears d->registered under vhub->lock before unregistering the gadget. Refuse the wakeup in ast_vhub_udc_wakeup() once d->registered is clear: the check and the schedule_work() are then atomic against the unbind, so a wakeup that passed before the flag was cleared is drained by the cancel_work_sync() after the del_dev loop, and one that arrives later returns without arming. Also move INIT_WORK() to the top of ast_vhub_probe(), since the probe error path reuses ast_vhub_remove() and would otherwise cancel a never-initialized work item. This issue was found by an in-house static analysis tool. Fixes: 7ecca2a ("usb/gadget: Add driver for Aspeed SoC virtual hub") Cc: stable@kernel.org Assisted-by: Codex:gpt-5.6 Co-developed-by: Song Li Signed-off-by: Song Li Signed-off-by: Fan Wu Reviewed-by: Benjamin Herrenschmidt Link: https://patch.msgid.link/20260908041740.613713-1-fanwu01@zju.edu.cn Signed-off-by: Greg Kroah-Hartman Changed files: drivers/usb/gadget/udc/aspeed-vhub/core.c drivers/usb/gadget/udc/aspeed-vhub/dev.c drivers/usb/gadget/udc/aspeed-vhub/hub.c drivers/usb/gadget/udc/aspeed-vhub/vhub.h 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=f343bfa3fc9f6255602d66f4a7dbe7ddef13ba41 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98766 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98766 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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: unknown Paranoid ActionableScore: 0 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: YES 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).