From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90311][LOW] thermal: hwmon: Remove hwmon class device along with its parent [ Upstream Date: Fri, 18 Sep 2026 01:36:44 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90311 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 4fa8915f40f744c6db2a3c25b2ae7d2dd64c77b4 List-Id: CVE: CVE-2026-90311 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: thermal: hwmon: Remove hwmon class device along with its parent [ Upstream Commit: 4fa8915f40f744c6db2a3c25b2ae7d2dd64c77b4 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4fa8915f40f744c6db2a3c25b2ae7d2dd64c77b4 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90311 Analysis date: Fri, 18 Sep 2026 01:36:44 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90311 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90311 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: LOW 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-2026-90311 LOW https://www.kernelcve.org/list/?q=CVE-2026-90311 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-667;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'A thermal hwmon class device could be registered under the first thermal zone of a given type while also exposing sysfs attributes for other thermal zones of the same type. If the parent thermal zone was removed, cleanup could be blocked by attributes belonging to another thermal zone and device removal could stop making progress. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over thermal driver unbind or device removal. The issue is not network reachable and is triggered through local device management paths. Impact is denial of service limited to removal or cleanup progress, with no clear evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES OOB LOCK INIT NOMEMCHK RACE HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 1 * Paranoid score: 1 * No floor or cap changed the score. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Positive signals: * +1 constrained local availability issue. The commit establishes that removal of the parent thermal zone can stop making progress because the shared hwmon class device still contains attributes for another thermal zone of the same type. Negative or limiting signals: * Host-admin-equivalent operation is positively indicated. The example trigger is unbinding the ACPI thermal driver from the underlying platform device, which is normally a host administrator device-management operation. * No Real UAF is established. The patch removes sysfs attributes and unregisters the hwmon device, but it does not show post-free object use, double release, stale RCU traversal, or refcount mutation through a dangling reference. * No controlled reclaim, arbitrary write, OOB access, information disclosure, or privilege escalation is demonstrated. * No direct network reachability is established. * No extra availability point is awarded because the only demonstrated consequence is the same cleanup/removal progress failure. * The race-related locking change is not scored as a separate corruption primitive because the supplied evidence describes interference with add/remove sysfs interface operations, not memory corruption. 3. Reachability analysis The practical trigger is local device-management activity, specifically removal or unbinding of a thermal zone parent device such as an ACPI thermal driver platform device. That is normally restricted to host administrator privileges. There is no evidence that an ordinary local user can perform the complete trigger sequence. There is no namespace-scoped capability path because thermal zone and hwmon sysfs device management are not meaningfully delegated through attacker-created namespaces in the supplied context. No prior attacker-controlled setup, public network exposure, or special rare hardware prerequisite is required beyond having multiple thermal zones of the same type, but the security-relevant removal operation remains host-admin controlled. The locking change prevents races between thermal_add_hwmon_sysfs and thermal_remove_hwmon_sysfs, but the patch does not establish a hard attacker-controlled timing race. 4. Primitive and severity interpretation The exact primitive is an invalid cleanup and lifetime association of a shared hwmon class device relative to its parent thermal zone. It is not a heap lifetime primitive. The affected objects are structured kernel/sysfs objects, but the demonstrated behavior is cleanup/removal progress being blocked, not stale-object exploitation. There is no concrete repeated release or refcount operation on the same dangling reference. PrimitiveClass is CLASS_C because the issue is primarily a local invalid-state availability problem without an independently useful corruption, ownership, authorization, or security-boundary primitive. The demonstrated consequence is denial of service limited to thermal zone or device removal progress. Speculative broader consequences are not supported by the patch. ImportantCandidate is NO because there is no memory corruption or boundary bypass requiring Important-vs-Moderate preservation. AutoDowngradeAllowed is YES because the issue is host-admin-triggered, cleanup-limited, and lacks unresolved exploitation leverage. 5. One-sentence report phrase A shared thermal hwmon device could block parent thermal zone removal when attributes from another zone of the same type remained attached, causing a host-admin-triggered local cleanup DoS without evidence of memory corruption or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: the patch supports only a host-admin-triggered cleanup/removal DoS with no UAF, refcount corruption, authorization bypass, information leak, or realistic privilege-escalation primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: thermal: hwmon: Remove hwmon class device along with its parent [ Upstream Commit: 4fa8915f40f744c6db2a3c25b2ae7d2dd64c77b4 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4fa8915f40f744c6db2a3c25b2ae7d2dd64c77b4 Changed files: drivers/thermal/thermal_hwmon.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=4fa8915f40f744c6db2a3c25b2ae7d2dd64c77b4 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90311 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90311 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:L/PR:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.4 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: 1 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).