From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46138][MODERATE REGULAR] Bluetooth: hci_event: Fix OOB read and infinite loop in hci_le_create_big_complete_evt Date: Thu, 28 May 2026 13:05:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46138 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: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 6cb7f67bc28da787499291a562d49a084d9c90cd List-Id: CVE: CVE-2026-46138 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: Bluetooth: hci_event: Fix OOB read and infinite loop in hci_le_create_big_complete_evt Commit: 6cb7f67bc28da787499291a562d49a084d9c90cd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6cb7f67bc28da787499291a562d49a084d9c90cd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46138 Analysis date: Thu, 28 May 2026 13:05:17 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A malformed Bluetooth LE Create BIG Complete controller event can cause an OOB read from `bis_handle[]` and leave a BIG connection in `BT_BOUND` state, leading to an infinite loop with `hci_dev_lock` held and a realistic DoS. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46138 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46138 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-46138 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-125;*CWE-835;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A malformed LE Create BIG Complete event can make the Bluetooth HCI event handler read past the valid bis_handle flex array when fewer BIS handles are present than bound BIG connections. The out-of-bounds value is then used as an HCI handle and may be rejected, leaving the connection in BT_BOUND state and causing the same connection to be found again in a loop while hci_dev_lock is held. For the CVSS the PR:N is used because a malicious or faulty controller response does not require privileges on the victim once the affected controller path is reachable. The issue is firmware or controller mediated and is not clearly a normal remote Bluetooth packet parsing bug. Impact is mainly denial of service through a stuck HCI event path or kernel lockup, with no demonstrated information disclosure or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4) MAYBE REMOTE WRITE OOB DANGER ERRORPATH NETWORK LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: **3** * Paranoid score: **4** * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown * Firmware-mediated external influence: **+1**. The malformed `LE_Create_BIG_Complete` event is supplied by the Bluetooth controller. * Reliable kernel crash / strong DoS: **+1**. The OOB value can keep the connection in `BT_BOUND` state and create an infinite loop while `hci_dev_lock` is held. * Availability impact realistic: **+1**. A stuck HCI event handler can hang Bluetooth processing and may affect system responsiveness. * Broad subsystem exposure, paranoid only: **+1**. Bluetooth is common, and this is in the HCI event path, although the specific BIG/BIS ISO path is more specialized. * Weak read-only OOB: **+0**. The primitive is an OOB read from a flex array, not an OOB write, UAF, double-free, or controlled overwrite. * No confidentiality signal: **+0**. The OOB bytes are used as an internal HCI handle and are not shown to be disclosed to userspace or a peer. * No integrity / LPE signal: **+0**. No write primitive or realistic privilege escalation path is shown. * Specific controller / feature condition: **0 to -1 considered**. The path requires affected Bluetooth controller behavior and BIG/BIS setup, but I do not apply a strong rare-hardware penalty because it is still in the main Bluetooth stack. ## 3. Reachability analysis The direct trigger is a malformed Bluetooth controller event, not a normal userspace syscall and not clearly an over-the-air Bluetooth packet parser. A malicious or faulty controller can trigger it without local privileges on the host once the affected controller path is active. A remote Bluetooth-adjacent attacker is only a paranoid possibility if they can cause the controller to emit the malformed BIG completion event, but that is not demonstrated by the patch. Namespaces and containers do not materially lower the trigger requirement because the critical input comes from the controller event stream. ## 4. Severity interpretation This behaves like a **borderline actionable Moderate** issue. The realistic impact is DoS through an infinite loop with `hci_dev_lock` held. The theoretical OOB read is real, but it is read-only and not shown to leak data or corrupt memory. There is no supported LPE primitive, so it should not be treated as Important without additional evidence of remote controller manipulation or disclosure. ## 5. One-sentence report phrase A malformed Bluetooth LE Create BIG Complete controller event can cause an OOB read from `bis_handle[]` and leave a BIG connection in `BT_BOUND` state, leading to an infinite loop with `hci_dev_lock` held and a realistic DoS. ## 6. Manual review recommendation **MANUAL CHECK RECOMMENDED** Manual review is recommended because this is a core Bluetooth HCI event path with controller-supplied malformed input and a lock-held infinite loop, but the current evidence supports DoS only and not information disclosure or privilege escalation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: hci_event: Fix OOB read and infinite loop in hci_le_create_big_complete_evt Commit: 6cb7f67bc28da787499291a562d49a084d9c90cd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6cb7f67bc28da787499291a562d49a084d9c90cd Commit description: hci_le_create_big_complete_evt() iterates over BT_BOUND connections for a BIG handle using a while loop, accessing ev->bis_handle[i++] on each iteration. However, there is no check that i stays within ev->num_bis before the array access. When a controller sends a LE_Create_BIG_Complete event with fewer bis_handle entries than there are BT_BOUND connections for that BIG, or with num_bis=0, the loop reads beyond the valid bis_handle[] flex array into adjacent heap memory. Since the out-of-bounds values typically exceed HCI_CONN_HANDLE_MAX (0x0EFF), hci_conn_set_handle() rejects them and the connection remains in BT_BOUND state. The same connection is then found again by hci_conn_hash_lookup_big_state(), creating an infinite loop with hci_dev_lock held. Fix this by terminating the BIG if in case not all BIS could be setup properly. Fixes: a0bfde1 ("Bluetooth: ISO: Add support for connecting multiple BISes") Cc: stable@vger.kernel.org Signed-off-by: ZhiTao Ou Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman Changed files: net/bluetooth/hci_event.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=6cb7f67bc28da787499291a562d49a084d9c90cd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46138 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46138 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:P/AC:L/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:N/I:N/A:H The Best / paranoid CVSS score: 5.3 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: 3 Paranoid ActionableScore: 4 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).