From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98109][MODERATE REGULAR] Bluetooth: hci_core: Fix race condition during device registration [ Upstream Date: Fri, 25 Sep 2026 12:19:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98109 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: b1faf348c29e6f8302ec7769cbf1c1ef05be014f List-Id: CVE: CVE-2026-98109 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: Bluetooth: hci_core: Fix race condition during device registration [ Upstream Commit: b1faf348c29e6f8302ec7769cbf1c1ef05be014f Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1faf348c29e6f8302ec7769cbf1c1ef05be014f Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98109 Analysis date: Fri, 25 Sep 2026 12:19:16 -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-2026-98109 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98109 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 REGULAR 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-2026-98109 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98109 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-665;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A race during HCI device registration can queue the power on work before the MSFT extension and its filter_lock mutex are fully initialized. For devices using HCI_QUIRK_RAW_DEVICE the work item can close the device concurrently with registration and msft_do_close can lock an uninitialized mutex, resulting in a DEBUG_LOCKS warning and potentially a kernel hang or crash. For the CVSS the PR:L is used because reliable triggering requires local ability to create register or control a suitable HCI device or equivalent delegated Bluetooth administration. The issue is not directly network reachable because it occurs in the local device registration path rather than through ordinary remote Bluetooth traffic. Impact is primarily denial of service. No confidentiality or integrity impact is established because the patch shows an initialization race and not a use after free out of bounds access or arbitrary memory write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES REMOTE OOB LOCK DANGER RACE NETWORK HARDWARE SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate**:: The score is identical because the patch establishes an initialization race and a DEBUG_LOCKS warning, but does not establish a real UAF, post-free access, controlled corruption, reliable kernel crash, information disclosure, integrity impact, or privilege escalation. 2. Signal breakdown * +1 Weak invalid-state kernel operation. The workqueue path can call mutex_lock on msft filter_lock after hdev msft_data is published but before mutex_init completes. This is an unsafe use-before-initialization of a synchronization object. * +0 WARN only. The supplied evidence demonstrates DEBUG_LOCKS_WARN_ON. A warning alone is not counted as reliable host-wide denial of service. * +0 Reliable kernel crash or strong DoS not awarded. A hang or crash is plausible for misuse of an uninitialized mutex, but the supplied trace shows a lock debugging warning rather than an actual panic, Oops, deadlock, or host failure. * +0 Real UAF not awarded. The msft object is allocated and prematurely published, but the evidence does not show that it is freed or released while a stale reference is later used. * +0 Controlled reclaim or object replacement not demonstrated. * +0 Arbitrary or directed kernel write not demonstrated. * +0 Confidentiality and integrity signals not awarded. There is no read-back, disclosure, unauthorized state modification, or security-boundary bypass. * +0 Remote reachability not established. The vulnerable path is HCI device registration and asynchronous local work execution, not ordinary Bluetooth packet processing. * +0 Local unprivileged trigger not awarded. The supplied material does not establish that an ordinary user can complete creation or registration of a suitable HCI_QUIRK_RAW_DEVICE HCI device. * -0 Race penalty not applied. Although the race window is short, the commit and syzbot report establish that concurrent execution is possible. The evidence does not establish that triggering is so rare or externally uncontrollable that a numeric reduction is justified. 3. Reachability analysis The affected sequence begins during local HCI device registration in hci_register_dev. The hdev power_on work item is queued before MSFT extension initialization completes. A device marked HCI_QUIRK_RAW_DEVICE can enter the HCI_UNCONFIGURED state, causing hci_power_on to close the device and invoke msft_do_close while registration is still executing. The immediate trigger depends on creating, registering, or controlling a suitable HCI device. The supplied patch does not establish whether this can be done by an ordinary local user, a user with delegated Bluetooth administration, a namespace-scoped capability, a privileged test interface, or only host administration. Therefore HostAdminRequired is UNKNOWN. NamespaceScopedPrivilege is UNKNOWN. Bluetooth and HCI objects can interact with namespaces in some configurations, but the supplied evidence does not show that all required stages, including suitable device creation, HCI registration, HCI_QUIRK_RAW_DEVICE state, and the asynchronous close path, can be completed from an attacker-controlled namespace. No prior firmware compromise, remote Bluetooth peer interaction, special external hardware, or public-network reachability is established by the patch. The issue is best treated as a local device-registration race whose practical reachability requires environment-specific confirmation. 4. Primitive and severity interpretation The exact primitive is a use-before-initialization race on msft filter_lock. The msft structure is allocated and exposed through hdev msft_data before mutex_init initializes its filter_lock. Concurrent power_on work can observe the published pointer and call msft_do_close, which attempts mutex_lock on the uninitialized lock. This is not an active structured-object UAF and not fixed stale storage. No object lifetime ends before later use. There is no first release, no dangling reference, no second put or refcount mutation, and no repeated lifetime operation. The demonstrated behavior is a DEBUG_LOCKS warning from mutex validation. A kernel hang, lock corruption, or crash may be possible depending on locking configuration and memory contents, but those consequences are not directly demonstrated. There is no patch-supported exploitation leverage beyond invalid synchronization state. PrimitiveClass is CLASS_C because the established behavior is invalid-state handling with warning or potential DoS impact, without a meaningful corruption, ownership, authorization, or lifetime primitive. ImportantCandidate is NO because the patch does not establish unresolved exploitation leverage beyond the invalid mutex use. AutoDowngradeAllowed is YES because no concrete UAF, write-like post-lifetime operation, security-boundary bypass, or controlled kernel corruption remains unresolved. Likely operational severity is Low to ordinary Moderate. It should be reviewed for actual affected deployment reachability, especially where untrusted actors can create virtual or raw HCI devices, but the supplied patch alone does not support Important classification. 5. One-sentence report phrase A race during Bluetooth HCI device registration can expose the MSFT filter_lock before mutex initialization, causing msft_do_close to lock an uninitialized mutex and trigger a DEBUG_LOCKS warning with possible local denial of service impact. 6. Manual review recommendation MANUAL CHECK RECOMMENDED The exact privilege boundary for creating or registering a suitable raw HCI device is unresolved, and product-specific Bluetooth virtualization or delegated device-management interfaces may affect practical reachability. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: hci_core: Fix race condition during device registration [ Upstream Commit: b1faf348c29e6f8302ec7769cbf1c1ef05be014f Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1faf348c29e6f8302ec7769cbf1c1ef05be014f Changed files: kernel/locking/mutex.c:821 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=b1faf348c29e6f8302ec7769cbf1c1ef05be014f ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98109 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98109 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:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 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: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).