From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64244][LOW] drivers/base/memory: set mem->altmap after successful device registration [ Upstream Date: Fri, 24 Jul 2026 12:19:02 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64244 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: 802e113cf120df7208e4c7e604950a85e87120a8 List-Id: CVE: CVE-2026-64244 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drivers/base/memory: set mem->altmap after successful device registration [ Upstream Commit: 802e113cf120df7208e4c7e604950a85e87120a8 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=802e113cf120df7208e4c7e604950a85e87120a8 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64244 Analysis date: Fri, 24 Jul 2026 12:19:02 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A memory hotplug cleanup ordering bug can leave mem altmap set after failed memory block registration, causing WARN_ON during device unregister and at most a local DoS on systems where WARN is fatal. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64244 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64244 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-2026-64244 LOW CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-703;CWE-754;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'The memory hotplug path could set mem altmap before the memory block was successfully registered. If registration then failed in __add_memory_block, for example during xa_store under memory pressure, cleanup through device_unregister could reach memory_block_release with mem altmap still set and trigger WARN_ON. For the CVSS the PR:L is used only for the paranoid interpretation where a local user may help trigger allocation failure through memory pressure while an automated hotplug component performs the privileged operation. The normal practical case is closer to PR:H because memory hotplug and altmap setup are administrative or platform controlled. The issue is not network reachable. Impact is denial of service at most, mainly when WARN is fatal or when repeated failures disrupt memory hotplug operations.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES WARNONLY SIMPLEFIX HARDWARE YES 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 Conservative signals: * Requires admin/root/device-management path: -2. Memory hotplug and altmap setup are normally controlled by privileged kernel or platform mechanisms, not ordinary users. * Rare/configuration-dependent path: -1. The issue requires memory hotplug with vmem_altmap and a failing registration path, e.g. xa_store failure under memory pressure. * WARN/state-cleanup issue: +1. The concrete failure is WARN_ON(mem->altmap) in memory_block_release after failed registration cleanup. Conservative score is effectively floored at 0 because the negative privilege and reachability constraints dominate. Paranoid signals: * Local unprivileged trigger assistance: +1. A local user may be able to contribute memory pressure while a privileged or automated virtio-mem or memory-hotplug operation is occurring. * Availability concern: +1. WARN_ON can become a practical DoS only on systems with panic_on_warn or similar policy. * Requires privileged hotplug operation: -1. Even in the paranoid model, the attacker likely does not directly invoke the vulnerable memory-hotplug path without some privileged or platform-driven action. Paranoid score: 1. No memory corruption signal is awarded. The patch only moves mem->altmap assignment after successful __add_memory_block registration and does not show UAF, OOB access, double free, stale callback, arbitrary write, info leak, or object replacement. ## 3. Reachability analysis The realistic trigger is a failed memory block registration in the memory hotplug path while altmap is involved. This is normally reachable through privileged platform or device-management flows such as virtio-mem, not through a normal unprivileged syscall path. Namespaces and containers do not materially lower the privilege requirement in typical deployments because memory hotplug is host-level device or platform management. A local unprivileged user might only assist indirectly by creating memory pressure, which is not enough for reliable triggering by itself. The path is not network reachable. It is also not a broad default user-facing interface. Exploitation conditions require a specific hotplug setup, altmap use, and an allocation or xa_store failure at the right point. Call-site confidence: medium. The relevant cleanup path is described in the commit message and the patch location is clear, but the full caller tree is not included in the input. ## 4. Severity interpretation This behaves like a Low or ordinary Moderate reliability issue, not an Important-class vulnerability. The demonstrated impact is a WARN during cleanup after a failed registration path. The main practical security concern is local DoS only if WARN is fatal or if repeated hotplug failures disrupt system operation. There is no supported privilege escalation path. There is no demonstrated confidentiality or integrity impact. The theoretical paranoid interpretation remains DoS-only and should not be upgraded into memory corruption or LPE. ## 5. One-sentence report phrase A memory hotplug cleanup ordering bug can leave mem altmap set after failed memory block registration, causing WARN_ON during device unregister and at most a local DoS on systems where WARN is fatal. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch shows a cleanup-ordering WARN without a concrete memory corruption primitive, security-boundary bypass, network reachability, or realistic privilege escalation path. This can be auto-closed or handled as non-urgent unless the target product uses panic_on_warn together with automated virtio-mem or memory-hotplug workflows. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drivers/base/memory: set mem->altmap after successful device registration [ Upstream Commit: 802e113cf120df7208e4c7e604950a85e87120a8 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=802e113cf120df7208e4c7e604950a85e87120a8 Changed files: drivers/base/memory.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=802e113cf120df7208e4c7e604950a85e87120a8 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64244 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64244 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:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 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).