From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90254][LOW] Bluetooth: hci_sync: free the advertising instance on the failure and cancel paths [ Upstream Date: Thu, 17 Sep 2026 19:31:13 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90254 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: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: c2019224a766245b7db39d87fdfe84c3fdc879d9 List-Id: CVE: CVE-2026-90254 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: Bluetooth: hci_sync: free the advertising instance on the failure and cancel paths [ Upstream Commit: c2019224a766245b7db39d87fdfe84c3fdc879d9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c2019224a766245b7db39d87fdfe84c3fdc879d9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90254 Analysis date: Thu, 17 Sep 2026 19:31:13 -0400 ActionableScore: 2 ActionableScore lower bound: 1 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-2026-90254 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90254 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-2026-90254 LOW https://www.kernelcve.org/list/?q=CVE-2026-90254 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'A small memory leak exists in the Bluetooth hci_sync advertising timeout path because a kmalloc buffer for the advertising instance can be queued without a destroy callback. If hci_cmd_sync_queue() fails or if a pending command sync entry is cancelled during controller unregister, the buffer is not released. For the CVSS the PR:L is used in the paranoid score because some systems may delegate Bluetooth management to a service account or container root, although the base score uses PR:H for normal administrative control. The issue is not network reachable and is triggered through local Bluetooth management operations rather than remote Bluetooth traffic. Impact is limited denial of service through gradual resource exhaustion. No memory corruption, information disclosure, or privilege escalation primitive is indicated.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES REMOTE SIMPLEFIX LEAK NETWORK LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1. No floor or cap applied. * Raw paranoid score: 2 * Paranoid score: 2. No floor or cap applied. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Conservative positive signals: * +1 Concrete persistent kernel resource/reference leak. The patch directly establishes that a kmalloc allocated advertising instance byte can be lost when hci_cmd_sync_queue() fails or when a queued command is cancelled without a destroy callback. Paranoid additional signal: * +1 Limited resource exhaustion potential. Repeated failure or cancellation of advertising timeout work could accumulate leaked kernel allocations, but the allocation is small and no immediate host-wide failure is shown. Non-awarded signals: * RealUAF not awarded. The bug is a leak, not post-free use. * Concrete repeated release/refcount not awarded. There is no first release followed by a second lifetime mutation on the same dangling reference. * Controlled reclaim not demonstrated. * Arbitrary write not demonstrated. * Confidentiality and integrity impact not awarded. * Remote reachability not established. This is not triggered by remote Bluetooth traffic in the supplied evidence. * Reliable kernel crash not awarded. The demonstrated issue is memory leakage, not panic or Oops. * ImportantCandidate not awarded because no corruption, boundary bypass, UAF, or strong unresolved exploitation primitive exists. 3. Reachability analysis The vulnerable path is in the Bluetooth hci_sync advertising timeout handling. A realistic trigger requires local ability to create or manage Bluetooth advertising state and to reach queue failure or cancellation paths such as controller unregister or command queue failure. The supplied evidence does not prove that an ordinary unprivileged local user can complete the trigger, and it also does not fully prove that host-admin-equivalent privilege is mandatory in every deployment, so HostAdminRequired is UNKNOWN. Bluetooth controller management is not meaningfully namespace-scoped from the supplied context. No network namespace or container-scoped capability path is established. No direct remote Bluetooth packet trigger is shown. No special rare hardware beyond a Bluetooth controller is required, but practical exposure depends on Bluetooth advertising being used and controllable. Race repeatability is not relevant here. This is an ordered failure/cancel cleanup bug, not a timing race. 4. Primitive and severity interpretation The exact primitive is a small persistent kernel memory leak of the allocated advertising instance buffer. The buffer is allocated in adv_timeout_expire() and should be released either by the queued sync callback path or by cleanup when queueing fails or a queued entry is cancelled. The old code used a NULL destroy callback and did not check the queue return value, so normal cleanup did not own and free the allocation on those paths. This is not active structured UAF and not fixed stale storage UAF. It is a resource ownership cleanup defect. The demonstrated consequence is gradual kernel memory loss. The speculative consequence is local DoS through sustained resource exhaustion, but the patch does not support memory corruption, information disclosure, privilege escalation, callback control, or arbitrary read/write. PrimitiveClass is CLASS_C because the issue is primarily resource leak / DoS behavior without an independently useful corruption primitive. ImportantCandidate is NO because the leak is small and no security-boundary or memory-corruption leverage is established. AutoDowngradeAllowed is YES because automatic downgrade would not discard an unresolved Important-grade primitive. 5. One-sentence report phrase A small memory leak in Bluetooth hci_sync advertising timeout handling can lose the allocated advertising instance buffer on queue failure or cancellation, causing only limited local resource exhaustion risk with no demonstrated memory corruption or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a small memory leak with no UAF, no repeated refcount mutation, no authorization bypass, no remote trigger, and no demonstrated host-wide crash. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: hci_sync: free the advertising instance on the failure and cancel paths [ Upstream Commit: c2019224a766245b7db39d87fdfe84c3fdc879d9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c2019224a766245b7db39d87fdfe84c3fdc879d9 Changed files: net/bluetooth/hci_sync.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=c2019224a766245b7db39d87fdfe84c3fdc879d9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90254 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90254 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:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS score: 3.3 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: 1 Paranoid ActionableScore: 2 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).