From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-98736][MODERATE 7.0] Bluetooth: hci_conn: Lock parent access during enhanced SCO setup Date: Sat, 24 Oct 2026 09:01:06 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-98736 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: 4 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 1239ef0fa809b5952fca679db3faa3e1c00e1dac List-Id: CVE: CVE-2026-98736 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: Bluetooth: hci_conn: Lock parent access during enhanced SCO setup Commit: 1239ef0fa809b5952fca679db3faa3e1c00e1dac Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1239ef0fa809b5952fca679db3faa3e1c00e1dac Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98736 Analysis date: Sat, 24 Oct 2026 09:01:06 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Borderline / manual review recommended Manual review required: YES Summary: A narrow Bluetooth workqueue race permits a demonstrated one-byte read from a freed ACL parent during SCO parameter selection, plausibly crashing the kernel without a shown write or reuse primitive. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98736 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98736 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-2026-98736 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98736 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=5 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in hci_enhanced_setup_sync allows the receive workqueue to unlink and free the ACL parent while the request workqueue still uses a previously loaded conn parent pointer. The demonstrated primitive is a one byte slab use after free read from parent features during enhanced SCO parameter selection. A local attacker able to initiate SCO activity may trigger a kernel crash by racing setup against ACL disconnection. A Bluetooth peer may help control disconnection timing, but the available evidence does not establish a fully remote trigger lacking a local SCO consumer. For the CVSS the PR:L value reflects the need for a local user or process able to reach Bluetooth SCO operations. AC:H reflects the required workqueue interleaving and narrow lifetime window. Availability impact is high due to a possible kernel crash. Limited confidentiality or integrity impact is retained only in the paranoid vector because slab reuse could influence the stale capability read, while no arbitrary write or reliable information disclosure is demonstrated. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.8 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 5 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE REMOTE READ OOB DANGER UAF NETWORK HARDWARE LINUS KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 PrimitiveClass=CLASS_B RealUAF=YES HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=UNKNOWN ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 2. * Conservative score: 4. Real-UAF floor 4 applied: 2 -> 4. * Raw paranoid score: 2. * Paranoid score: 4. The same floor applies; no additional exploit primitive is supported. * Final recommended bucket: **Borderline / manual review recommended**:: 2. Signal breakdown * +2 Real UAF: the receive worker can free the ACL parent after the request worker loads `conn->parent`, followed by a demonstrated one-byte read from freed `parent->features[0][3]`. * +1 Reliable kernel crash/DoS: the slab UAF can plausibly produce an Oops or kernel crash. * -1 Hard race: exploitation requires a narrow workqueue interleaving; the demonstrated KASAN result used an added 40 ms delay. * Floor 4: this is an actual stale use of an active structured object, not fixed stale storage, and host-admin-only reachability is not proven. * No structured stale-object leverage: the stale feature byte affects codec/parameter selection, but attacker-controlled reclaim, replacement contents, pointers, callbacks, or a later corrupting operation are not shown. * No OOB write, repeated release, arbitrary write, disclosure, C/I impact, or additional availability effect is established. * NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write. * B4-PENDING does not apply: no authorization decision is changed from DENY to ALLOW. 3. Reachability analysis A local process must initiate SCO setup while ACL disconnection races the queued setup work; a Bluetooth peer may influence disconnection timing. The complete socket permission and capability requirements are not shown, so below-host-admin reachability, host UID 0 requirements, and namespace-scoped privilege remain unknown. A fully remote trigger is not established. No unusual hardware beyond an applicable Bluetooth setup is evidenced. 4. Primitive and severity reading The primitive is a read-only slab UAF of an active ACL-parent object during normal SCO setup, not a cleanup-only dereference. The consumed stale byte selects enhanced-SCO parameters, but no post-free write, lifetime mutation, controlled reuse, or security-boundary crossing is shown. This is CLASS_B because the lifetime violation is concrete, while the demonstrated practical consequence is crash/DoS. Important-grade leverage is not materially evidenced, so automatic Moderate handling remains permissible after review. 5. One-sentence report phrase A narrow Bluetooth workqueue race permits a demonstrated one-byte read from a freed ACL parent during SCO parameter selection, plausibly crashing the kernel without a shown write or reuse primitive. 6. Manual review advice MANUAL CHECK RECOMMENDED Confirm product-specific SCO socket permissions and whether an attacker can reliably drive both setup and disconnection without privileged assistance. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: hci_conn: Lock parent access during enhanced SCO setup Commit: 1239ef0fa809b5952fca679db3faa3e1c00e1dac Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1239ef0fa809b5952fca679db3faa3e1c00e1dac Commit description: Bluetooth: hci_conn: Lock parent access during enhanced SCO setup hci_enhanced_setup_sync() runs on the request workqueue without the hci_dev_lock held by its caller when setup was queued. Its CVSD capability check and find_next_esco_param() dereference conn->parent while the receive workqueue can unlink and release that parent. The following interleaving can cause a use-after-free: hci_enhanced_setup_sync() hci_disconn_complete_evt() load conn->parent hci_dev_lock() hci_conn_del(ACL parent) unlink SCO child drop link's parent reference clear child->parent release ACL parent bt_link_release() kfree(parent) hci_dev_unlock() read parent->features[0][3] The reference held for the queued SCO child does not keep its ACL parent alive after unlinking. Commit 42de40a ("Bluetooth: hci_conn: fix the SCO setup context lifetime") protects the child stored in the queued context, but leaves these parent accesses unprotected. With a 40 ms diagnostic delay after loading conn->parent, an instrumented kernel based on fd179f8 , which already contains 42de40a , reported: BUG: KASAN: slab-use-after-free in hci_enhanced_setup_sync+0xda5/0xdf0 Read of size 1 at addr ffff888102204047 by task kworker/u17:0/93 Call Trace: hci_enhanced_setup_sync+0xda5/0xdf0 hci_cmd_sync_work+0x13c/0x290 process_one_work+0x6b4/0x10e0 Allocated by task 92: __hci_conn_add+0x304/0x1df0 hci_connect_acl+0x349/0x3e0 hci_connect_sco+0x3b/0x9a0 sco_sock_connect+0x475/0xca0 Freed by task 94: kfree+0x121/0x3c0 bt_link_release+0x79/0xa0 device_release+0xc8/0x240 kobject_put+0x14d/0x280 hci_conn_del+0x524/0xe30 hci_disconn_complete_evt+0x403/0x8c0 hci_event_packet+0x71b/0xb20 hci_rx_work+0x293/0x730 The accessed address is 71 bytes into the freed ACL parent, at its features[0][3] byte; the queued SCO child is a different object. The diagnostic preserves the loaded parent across the delay, matching the unmodified compiled capability check, and does not change the parent references or teardown path. Hold hci_dev_lock() across the codec switch, including every call to find_next_esco_param(), and release it on all selection errors. Keep configure_datapath_sync() outside the critical section because it waits for HCI events. Preserve parameter selection and existing return values. Fixes: e07a06b ("Bluetooth: Convert SCO configure_datapath to hci_sync") Cc: stable@vger.kernel.org Assisted-by: GPT-6-Astra Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman 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=1239ef0fa809b5952fca679db3faa3e1c00e1dac ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-98736 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98736 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:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 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: 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).