From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98762][MODERATE 7.0] USB: dwc2: shut down wakeup timer before freeing HCD state [ Upstream Date: Mon, 19 Oct 2026 02:09:45 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98762 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 441be312fce927443eae2821f502344d953c38bb List-Id: CVE: CVE-2026-98762 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: USB: dwc2: shut down wakeup timer before freeing HCD state [ Upstream Commit: 441be312fce927443eae2821f502344d953c38bb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=441be312fce927443eae2821f502344d953c38bb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98762 Analysis date: Mon, 19 Oct 2026 02:09:45 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A teardown race allows the DWC2 wakeup timer callback to access and potentially rearm against released HCD state, creating a constrained use after free that can crash the kernel during initialization failure or device removal. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98762 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98762 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-98762 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98762 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 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-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A teardown race exists because dwc2_wakeup_detected can access DWC2 host state and rearm the wakeup timer while dwc2_hcd_free is releasing host owned resources. The previous timer deletion did not synchronize with a running callback and did not prevent that callback from queuing the timer again. This creates a potential use after free that can cause a kernel crash and local denial of service. For the CVSS the PR:L value is used for the paranoid score because reduced capability root, a device management service, or a container with delegated driver control may be able to initiate the relevant HCD teardown without having unrestricted host root privileges. The realistic base case is PR:H because driver unbind, module removal, and normal HCD removal are generally administrator controlled. The issue is not network reachable. A connected USB device may influence wakeup activity, but the available code does not prove that an external device alone can reliably initiate HCD teardown. Impact is at least a local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to the potential use after free and should be reviewed manually. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. 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 INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 2 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 Borderline / manual review recommended (with actual score 3) MAYBE USB INIT SIMPLEFIX ERRORPATH TIMER LINUS INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 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: 2 * Conservative score: 2 * Raw paranoid score: 3 * Paranoid score: 3 * No score floor or cap was applied. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown Conservative signals: * +2 Real UAF or lifetime violation. `dwc2_wakeup_detected()` can continue accessing host-owned DWC2 state after teardown has started freeing that state. The callback can also rearm its timer. * +1 Realistic kernel crash or strong DoS. Access to released host state can cause an invalid dereference, Oops, or panic. * -1 One-shot teardown timing. The callback must overlap HCD initialization failure or removal, and the supplied evidence does not show that an attacker can repeatedly control both sides of the race. * Total: 2. Paranoid signals: * +2 Real UAF or lifetime violation. * +1 Realistic kernel crash or strong DoS. * The timing penalty is withheld because the callback can rearm the timer, potentially extending the stale-callback condition beyond a single timer invocation. * Total: 3. Important non-awarded signals: * No controlled reclaim, attacker-controlled replacement, arbitrary write, disclosure, callback hijack, or privilege escalation is established. * Structured stale-object leverage is not awarded. The stale storage belongs to a fixed driver and HCD context, and no attacker-shaped replacement state is shown. * No repeated release or refcount signal exists. There is no demonstrated first release followed by a second lifetime mutation through the same dangling reference. * No extra availability point is awarded for the same possible kernel crash. * Remote or malicious-USB-only triggering is not established. * NEW52 B5-R does not apply because no retry-accumulated heap OOB write exists. * NEW53 B3-PENDING does not apply because no shared-backing write exists. * V33 and V32 do not apply because no attacker-influenced active checksum or networking metadata corruption exists. * B4 authorization-state preservation does not apply because no authorization decision is changed from DENY to ALLOW. 3. Reachability analysis The vulnerable overlap occurs during HCD initialization failure or normal HCD removal. A host administrator can normally initiate driver unbind or removal, but the complete attacker-controlled trigger is not established because the initialization error path and wakeup timing may also depend on device or platform events. Therefore `HostAdminRequired=UNKNOWN` rather than YES or NO. A connected USB device may influence wakeup activity, but the supplied evidence does not show that such a device can independently initiate HCD teardown or reliably win the race. No network trigger exists. DWC2 is commonly integrated into embedded or SoC platforms, but hardware presence alone does not justify a rare-hardware penalty. No complete user-namespace or device-namespace trigger chain is demonstrated. Prior privileged configuration and below-host-admin delegated device management remain unresolved. 4. Primitive and severity interpretation The exact primitive is asynchronous post-lifetime access. A timer callback can access DWC2 host-owned state while `dwc2_hcd_free()` releases that state, and ordinary `timer_delete()` neither waits for the callback nor prevents timer rearming. This is a real CLASS_B lifetime violation involving fixed driver-owned state. It is teardown-specific rather than a general attacker-controlled active-object replacement primitive. The demonstrated practical consequence is kernel crash or local DoS. Confidentiality, integrity, controlled post-free reuse, and privilege escalation are speculative and unsupported by the supplied call path. There is no concrete repeated release or refcount mutation. The fix instead restores synchronization by shutting down the timer before freeing HCD resources. `ImportantCandidate=NO` because meaningful exploitation leverage beyond a stale callback and crash is not established. `AutoDowngradeAllowed=YES` because this is a constrained fixed-state teardown UAF without controlled reclaim, post-free payload control, repeated lifetime mutation, or a demonstrated security-boundary crossing. Operational severity is borderline Moderate with manual review recommended due to the real UAF. 5. One-sentence report phrase A teardown race allows the DWC2 wakeup timer callback to access and potentially rearm against released HCD state, creating a constrained use after free that can crash the kernel during initialization failure or device removal. 6. Manual review recommendation MANUAL CHECK RECOMMENDED The lifetime violation is concrete, but available evidence supports a constrained teardown UAF and crash risk rather than an Important-grade exploitation primitive. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: USB: dwc2: shut down wakeup timer before freeing HCD state [ Upstream Commit: 441be312fce927443eae2821f502344d953c38bb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=441be312fce927443eae2821f502344d953c38bb Changed files: drivers/usb/dwc2/hcd.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=441be312fce927443eae2821f502344d953c38bb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98762 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98762 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:N/I:N/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: 2 Paranoid ActionableScore: 3 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).