From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53031][MODERATE 7.0] bpf: Validate node_id in arena_alloc_pages() [ Upstream Date: Thu, 25 Jun 2026 10:15:22 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53031 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 31d3b4b28e55835646d6829d60023f730dd34e85 List-Id: CVE: CVE-2026-53031 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: bpf: Validate node_id in arena_alloc_pages() [ Upstream Commit: 31d3b4b28e55835646d6829d60023f730dd34e85 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31d3b4b28e55835646d6829d60023f730dd34e85 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53031 Analysis date: Thu, 25 Jun 2026 10:15:22 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: Missing validation of an attacker supplied BPF arena NUMA node ID can send invalid or offline node values into the kernel allocation path, causing local DoS and requiring manual review for possible allocator-internal corruption impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53031 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53031 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-2026-53031 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-129;*CWE-20;*CWE-787;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.8';DESCR 'arena_alloc_pages accepts an attacker controlled node_id and passed it into the NUMA allocation path without validating the node range or online state. A local user with the ability to create and use BPF arena can supply an invalid or offline node id, which may make the kernel allocation path index invalid NUMA node data and crash. For the CVSS the PR:L is used for the paranoid score because triggering requires local BPF capability or an environment where BPF use is delegated to a less privileged service or user, but it does not require full host root in all deployments. The issue is not network reachable. Base impact is local denial of service via kernel crash. In the paranoid interpretation, invalid NUMA node indexing in the page allocator path is a memory corruption candidate, so confidentiality and integrity impact may be possible and the issue should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) MAYBE OOB BPF SIMPLEFIX LINUS KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Weak or indirect corruption candidate: +1. `node_id` is attacker influenced through the BPF arena allocation path and was passed into NUMA/page allocation without range or online-node validation. * Weak LPE concern: +1. Invalid NUMA node selection may reach allocator internals, but the patch does not show a controlled write, reclaim primitive, UAF, or object-confusion primitive. * Reliable kernel crash / strong DoS: +1. Invalid or offline node IDs can plausibly lead to allocator faults, WARN/BUG paths, NULL dereference, or invalid per-node data access. * Local high-control kernel data-plane API: +1. BPF arena is a rich local kernel API where users can shape allocation requests. * Broad/common subsystem exposure: +1. BPF is widely deployed, although BPF arena use is more specialized and typically gated. * Capability-gated local access: -1. Triggering usually requires BPF privileges such as CAP_BPF/CAP_SYS_ADMIN or a delegated BPF-capable service context, so this is not ordinary unprivileged local access. Paranoid additional interpretation: * Privileged allocator-internal sink: +1. The unchecked value enters trusted NUMA/page allocator paths, so manual review is justified even without a demonstrated exploit primitive. ## 3. Reachability analysis The bug is local only. It is not network reachable. A realistic trigger requires the ability to create and use BPF arena functionality, which is normally restricted by BPF capability policy or by privileged service/container configuration. Namespaces and delegated BPF setups matter because a reduced-capability service, container root, or user with BPF access may be below full host root but still able to reach this path. The affected subsystem is not a default unauthenticated interface, but BPF is common enough that the issue should not be treated as rare hardware-only or unreachable. ## 4. Severity interpretation This is more than an ordinary low-priority DoS because unchecked `node_id` flows into allocator internals from a high-control BPF API. The realistic impact is local kernel crash or allocator failure. The theoretical escalation concern is weaker than a proven UAF/OOB write because there is no clear attacker-controlled overwrite target or payload in the patch. Therefore this fits Actionable Moderate rather than automatic Important, with manual review recommended to confirm whether invalid NUMA node handling can become memory corruption beyond crash. ## 5. One-sentence report phrase Missing validation of an attacker supplied BPF arena NUMA node ID can send invalid or offline node values into the kernel allocation path, causing local DoS and requiring manual review for possible allocator-internal corruption impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the bug is reachable through BPF arena and affects allocator/NUMA internals. The demonstrated impact is likely DoS, but the invalid-index path is serious enough to verify whether it can produce memory corruption or privilege escalation in affected kernel configurations. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: bpf: Validate node_id in arena_alloc_pages() [ Upstream Commit: 31d3b4b28e55835646d6829d60023f730dd34e85 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31d3b4b28e55835646d6829d60023f730dd34e85 Changed files: kernel/bpf/arena.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=31d3b4b28e55835646d6829d60023f730dd34e85 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53031 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53031 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:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.8 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: 4 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: 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).