From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74302][MODERATE 7.0] Bluetooth: hci_core: Fix UAF in hci_unregister_dev() [ Upstream Date: Sat, 15 Aug 2026 13:51:03 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74302 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 48c7ad6afcc58c2cda11fed39791708103b6a644 List-Id: CVE: CVE-2026-74302 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: Bluetooth: hci_core: Fix UAF in hci_unregister_dev() [ Upstream Commit: 48c7ad6afcc58c2cda11fed39791708103b6a644 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=48c7ad6afcc58c2cda11fed39791708103b6a644 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74302 Analysis date: Sat, 15 Aug 2026 13:51:03 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: Bluetooth HCI device unregister can free `hci_dev` while `cmd_timer` or `ncmd_timer` delayed work is still pending, allowing a teardown race to dereference freed memory including `hdev->reset` and causing at least local kernel crash with potential UAF security impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74302 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74302 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-2026-74302 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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:L/I:L/A:H';BEST CVSS score: '7';DESCR 'Bluetooth hci_unregister_dev can free hci_dev while cmd_timer or ncmd_timer delayed work is still armed. If one of these timeouts fires during teardown, the callback may dereference freed hci_dev memory including the hdev reset function pointer, which makes this a use-after-free candidate and not just a warning. For the CVSS the PR:L is used for the paranoid score because a reduced capability local process with Bluetooth management rights or delegated device control may be able to reach teardown or reset paths, while typical full device unregister remains administrator controlled. The issue is not directly network reachable over Bluetooth alone because the vulnerable operation is local device teardown. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to use-after-free around a function pointer. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES REMOTE UAF NETWORK TIMER HARDWARE DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum** ## 2. Signal breakdown Conservative signals: * Generic memory corruption: +2. The commit explicitly describes a use-after-free in `hci_unregister_dev()`. * Real lifetime corruption: +1. Delayed work items can outlive the `hci_dev` object teardown. * Reliable kernel crash / strong DoS: +1. A timeout callback can dereference freed memory during teardown. * Weak LPE concern: +1. The UAF involves dereferencing freed `hci_dev` memory including `hdev->reset`, a function pointer, but no controlled reclaim or replacement primitive is demonstrated. * Hard or unreliable race / special timing required: -1. The timeout must fire during the unregister/free window. * Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering usually requires local device unregister, driver unload, device removal, or Bluetooth device-management control. Conservative total: 3 Paranoid adjustment: * Do not apply the full -2 privilege penalty. In some environments Bluetooth management, device control, container delegation, service accounts, or reduced-capability root may make this less than full host-root control. * Keep race penalty: -1. * Keep weak LPE concern because the stale object contains a callback/function-pointer field. Paranoid total: 5 ## 3. Reachability analysis The vulnerable path is local device teardown in Bluetooth HCI core, not normal remote Bluetooth packet processing. A remote Bluetooth peer does not appear to directly call `hci_unregister_dev()`. Realistic triggering usually requires local control over HCI device lifecycle, driver removal, device unplug, reset/unregister paths, or a privileged management context. Namespaces and containers may matter if Bluetooth device-management capabilities are delegated, but in typical deployments this remains an administrator-controlled path. The race window is narrow because the delayed work must fire while `hci_dev` is being torn down. Call-site confidence: high. The patch and commit directly identify `hci_unregister_dev()`, the two delayed work items, the freed `hci_dev`, and the callback dereference. ## 4. Severity interpretation This is more than an ordinary Moderate cleanup because the patch fixes a real UAF in an async lifetime path and mentions dereference of a function pointer. Realistic impact is most likely local DoS through kernel crash. Privilege escalation is not demonstrated, but the UAF around `hdev->reset` is enough to require manual review and avoid auto-close. This should be treated as Actionable Moderate at minimum. It is not a strong Important candidate without evidence of attacker-controlled reclaim, object replacement, or a reliable callback-control primitive. ## 5. One-sentence report phrase Bluetooth HCI device unregister can free `hci_dev` while `cmd_timer` or `ncmd_timer` delayed work is still pending, allowing a teardown race to dereference freed memory including `hdev->reset` and causing at least local kernel crash with potential UAF security impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: explicit UAF, async lifetime bug, race-dependent teardown path, and stale dereference involving a function pointer make this unsafe to auto-close even though the realistic trigger is local and usually privileged. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: hci_core: Fix UAF in hci_unregister_dev() [ Upstream Commit: 48c7ad6afcc58c2cda11fed39791708103b6a644 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=48c7ad6afcc58c2cda11fed39791708103b6a644 Changed files: net/bluetooth/hci_core.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=48c7ad6afcc58c2cda11fed39791708103b6a644 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74302 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74302 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:L/I:L/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: 3 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: NO 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).