From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90255][MODERATE 7.0] Bluetooth: hci_conn: fix the SCO setup context lifetime [ Upstream Date: Thu, 17 Sep 2026 20:25:34 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90255 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 37cfec41365c826d5496ef5d00c9e215eee53aa2 List-Id: CVE: CVE-2026-90255 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: Bluetooth: hci_conn: fix the SCO setup context lifetime [ Upstream Commit: 37cfec41365c826d5496ef5d00c9e215eee53aa2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=37cfec41365c826d5496ef5d00c9e215eee53aa2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90255 Analysis date: Thu, 17 Sep 2026 20:25:34 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90255 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90255 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-2026-90255 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90255 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-401;*CWE-664;CWE-362;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A lifetime bug in the Bluetooth SCO setup path can leave a queued hci_enhanced_setup_sync callback holding a bare hci_conn pointer after the connection object has been freed. This is a use-after-free candidate because the queued work may later dereference the stale connection pointer while processing the setup context. A nearby Bluetooth peer may be able to influence SCO setup and teardown timing, although reliable triggering is likely timing dependent and configuration dependent. For the CVSS the PR:N is used because the paranoid interpretation assumes an adjacent attacker does not need a local account on the target and only needs Bluetooth reachability to the affected path. Impact is at least denial of service via kernel crash. In the paranoid case, the UAF class can justify C:H/I:H/A:H because stale kernel object reuse may become exploitable beyond a crash and should not be autoclosed without manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES REMOTE LEAK UAF NETWORK KPANIC DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4 * Raw paranoid score: 5 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: No floor or cap changed the conservative score. No floor or cap changed the paranoid score. 2. Signal breakdown Conservative positive signals: * +2 Real UAF / active lifetime violation. The queued SCO setup context stores a bare `hci_conn` pointer, and the commit states that the connection can be freed while the work is still queued. * +1 Reliable kernel crash / strong DoS. A later queued callback may dereference the stale `hci_conn` pointer in kernel context. * +1 Concrete persistent kernel resource/reference leak. A queued `conn_handle_t` entry cancelled without a destroy callback leaks because `_hci_cmd_sync_cancel_entry()` does not release `entry->data`. Paranoid additional signal: * +1 Firmware-mediated or adjacent external influence. Bluetooth SCO setup and connection teardown may be influenced by an adjacent Bluetooth peer, but complete attacker-controlled reachability is not fully established from the supplied patch alone. Non-awarded signals: * Controlled reclaim was not demonstrated. * Arbitrary read/write was not demonstrated. * Callback or function-pointer control was not demonstrated. * Structured stale-object exploitation leverage was not awarded because the patch establishes stale `hci_conn` dereference/lifetime misuse, but not attacker-shaped replacement object consumption. * Weak LPE was not separately awarded merely because this is a UAF. * Concrete repeated release/refcount was not awarded. The bug is missing lifetime hold plus stale dereference, not a visible second `put` on the exact same dangling reference. * Extra Availability was not awarded because the same crash/DoS is already counted once. * Confidentiality and integrity were not awarded in ActionableScore because no concrete disclosure, overwrite, credential change, or security-boundary bypass is established. * Race/timing penalty was not applied. The issue involves queued asynchronous work, but the evidence does not prove a narrow one-shot timing window that should be penalized. * Host-admin penalty was not applied. The supplied evidence does not positively establish that host-admin-equivalent privilege is required for the complete vulnerable sequence. Repeated-release/refcount checklist: * First release can end lifetime: not applicable as a scored repeated-release primitive. * Exact same reference survives to a second lifetime mutation: not established. * Second operation is a real lifetime/refcount mutation: not established. * +1 Concrete repeated release/refcount awarded: no. * Paranoid repeated-refcount leverage awarded: no. * FLOOR 5 from repeated-release rule applied: no. 3. Reachability analysis The affected path is Bluetooth SCO setup through queued HCI synchronous work. A nearby Bluetooth peer may influence SCO connection setup and teardown behavior, but the supplied patch does not fully establish that an adjacent attacker alone can perform the complete trigger sequence reliably. The context leak path is clearly reached when queued entries are cancelled, including controller unregister cleanup. Controller unregister is likely local management activity, but the UAF statement is broader: the connection can be freed while the work is queued, and `hci_conn_del()` does not dequeue this wrapper case. HostAdminRequired is UNKNOWN because the supplied evidence does not prove either full host-admin requirement or complete below-host-admin reachability. NamespaceScopedPrivilege is NO because no namespace-scoped privilege model is involved in this Bluetooth path. No prior privileged setup is proven beyond having Bluetooth enabled and the relevant SCO path available. Special Bluetooth hardware/controller availability is required in practice, but this is not treated as rare hardware by itself. Race repeatability is unresolved rather than proven hard. 4. Primitive and severity interpretation The exact primitive is a lifetime bug where queued work keeps a stale pointer to an active structured kernel object, `struct hci_conn`. This is not fixed stale storage. It is an active object used by the Bluetooth connection setup path. The demonstrated issue is stronger than a pure memory leak because the queued callback can later consume a connection pointer after the connection has been freed. The demonstrated consequence is at least kernel crash or DoS. The speculative consequence is broader exploitation through stale kernel object reuse, but controlled reclaim or attacker-shaped replacement has not been shown. PrimitiveClass is CLASS_B because a real kernel lifetime/UAF primitive is established, but no Class A primitive such as controlled reclaim, arbitrary write, callback hijack, or demonstrated privilege escalation is established. ImportantCandidate is YES because this is an active-object UAF in a wireless protocol path with unresolved exploitation leverage beyond ordinary cleanup-only crash behavior. AutoDowngradeAllowed is NO because automatically closing it as ordinary Moderate would discard a concrete unresolved kernel lifetime primitive. Likely operational severity is Actionable Moderate, with Strong Important review warranted if adjacent attacker reachability or useful stale-object reuse can be confirmed. 5. One-sentence report phrase A Bluetooth SCO setup lifetime bug can leave queued work holding a stale `hci_conn` pointer after the connection is freed, creating a real kernel UAF candidate with at least DoS impact and requiring manual review for possible stronger exploitation. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch establishes a real active-object lifetime violation involving `hci_conn`, and the reachable Bluetooth/SCO context makes automatic downgrade unsafe even though controlled reclaim or LPE is not demonstrated. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: hci_conn: fix the SCO setup context lifetime [ Upstream Commit: 37cfec41365c826d5496ef5d00c9e215eee53aa2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=37cfec41365c826d5496ef5d00c9e215eee53aa2 Changed files: net/bluetooth/hci_conn.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=37cfec41365c826d5496ef5d00c9e215eee53aa2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90255 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90255 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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.5 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: 4 Paranoid ActionableScore: 5 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).