From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72067][LOW] cpu: hotplug: Preserve per instance callback errors Date: Sat, 15 Aug 2026 20:00:52 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72067 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: 1 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: fe9c8d641f6991614d1229a3ffd3e33b879bba9c List-Id: CVE: CVE-2026-72067 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: cpu: hotplug: Preserve per instance callback errors Commit: fe9c8d641f6991614d1229a3ffd3e33b879bba9c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe9c8d641f6991614d1229a3ffd3e33b879bba9c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72067 Analysis date: Sat, 15 Aug 2026 20:00:52 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A CPU hotplug rollback path could hide the original per-instance callback failure and make a failed transition appear successful, causing privileged local availability or state-consistency impact without evidence of memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72067 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72067 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-2026-72067 LOW CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-703;CWE-754;CWE-252;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'CPU hotplug per instance callback failure handling could incorrectly report success because the rollback path reused the same return variable as the original failed callback. A successful rollback could hide the original error and make a failed hotplug transition look successful, leaving higher level CPU hotplug logic with an incorrect result. For the CVSS the PR:H is used because CPU hotplug transitions and related state changes normally require administrator level control on the host. The issue is not network reachable and is triggered through local CPU hotplug control paths rather than packet or remote input. Impact is mainly availability risk from inconsistent hotplug state or failed recovery handling, with no concrete memory corruption primitive indicated by the patch.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES DANGER INIT SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown Triggered signals: * Availability impact realistic: +1 The bug can make a failed CPU hotplug transition appear successful, which may leave higher-level CPU hotplug logic with an incorrect result. * Broad/default/core kernel subsystem: +1 CPU hotplug is core kernel infrastructure, but the affected path is not normally exposed to unprivileged users. Subtracted signals: * Requires admin/root/CAP_SYS_ADMIN-like control in typical deployments: -2 Triggering CPU hotplug state transitions normally requires administrator-level host control. Not triggered: * No remote reachability. * No local unprivileged trigger. * No UAF, double-free, OOB write, refcount corruption, type confusion, or arbitrary write. * No practical privilege escalation path. * No sensitive data exposure. * No strong demonstrated crash primitive. ## 3. Reachability analysis The bug is reachable through CPU hotplug transition handling, not through packet processing, syscalls available to ordinary users, or a network protocol. In typical deployments, online/offline CPU management and related hotplug state changes require root or equivalent administrative control. Containers or namespaces normally do not provide direct authority over host CPU hotplug, so namespace delegation does not materially reduce PR in the usual case. The path is part of core kernel infrastructure, but realistic attacker reachability is narrow and privileged. The patch only preserves the original callback error across rollback. It does not show memory lifetime corruption or attacker-controlled data-plane behavior. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like correctness and availability issue, not an Important-class kernel vulnerability. The theoretical concern is inconsistent CPU hotplug state or incorrect success reporting after a failed per-instance callback. The realistic evidence supports only privileged local availability impact, with no demonstrated memory corruption, confidentiality impact, integrity impact, or privilege escalation. ## 5. One-sentence report phrase A CPU hotplug rollback path could hide the original per-instance callback failure and make a failed transition appear successful, causing privileged local availability or state-consistency impact without evidence of memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed for practical triage unless the affected product exposes CPU hotplug control to reduced-privilege service accounts or container roots. The patch is a privileged local error-handling fix with no concrete corruption primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: cpu: hotplug: Preserve per instance callback errors Commit: fe9c8d641f6991614d1229a3ffd3e33b879bba9c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe9c8d641f6991614d1229a3ffd3e33b879bba9c Commit description: cpuhp_invoke_callback() unwinds earlier callbacks for the same hotplug state when one instance fails. The rollback path currently reuses ret, so a successful rollback can hide the original error and make the failed transition look successful. Keep the rollback result separate from the original error. Fixes: 724a868 ("smp/hotplug: Callback vs state-machine consistency") Signed-off-by: Bradley Morgan Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260619163719.12103-1-include@grrlz.net Signed-off-by: Greg Kroah-Hartman Changed files: kernel/cpu.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=fe9c8d641f6991614d1229a3ffd3e33b879bba9c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72067 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72067 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:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.1 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: 0 Paranoid ActionableScore: 1 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).