From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90304][LOW] ARM: 9484/1: enable interrupts when unhandled user faults are triggered [ Upstream Date: Fri, 18 Sep 2026 05:59:40 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90304 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: 8d7cbc6df9632d334b21c4be66ccdde76a08fb13 List-Id: CVE: CVE-2026-90304 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: ARM: 9484/1: enable interrupts when unhandled user faults are triggered [ Upstream Commit: 8d7cbc6df9632d334b21c4be66ccdde76a08fb13 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d7cbc6df9632d334b21c4be66ccdde76a08fb13 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90304 Analysis date: Fri, 18 Sep 2026 05:59:40 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90304 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90304 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-2026-90304 LOW https://www.kernelcve.org/list/?q=CVE-2026-90304 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;CWE-703;CWE-755;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'On 32 bit ARM PREEMPT_RT kernels, an unhandled user Data Abort or Prefetch Abort can reach force_sig_fault while local interrupts remain disabled. A local user program can trigger the affected path by executing a bkpt instruction when CONFIG_PERF_EVENTS is disabled, causing signal delivery to run in an invalid interrupt context. This can produce kernel warnings, scheduling or locking failures, and potentially a system stall or denial of service. For the CVSS the PR:L is selected because an unprivileged local process is required to execute the faulting instruction, while no administrative capability is normally needed. The issue is not directly network reachable and requires local code execution on an affected ARM system. Impact is limited to availability because the examined path provides no UAF, OOB access, information disclosure, or controlled memory write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) SKIP CVE-2026-90304 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE SIMPLEFIX HARDWARE MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 0 * Conservative score: 0 * Raw paranoid score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap was applied. 2. Signal breakdown Conservative signals: * +1 Local unprivileged trigger. An ordinary local process can execute `bkpt` and reach the unhandled user-fault path without administrative capabilities. * -1 Rare and difficult-to-reach configuration. The documented trigger requires 32-bit ARM, PREEMPT_RT, and `CONFIG_PERF_EVENTS=n`. An attacker cannot establish these build and execution prerequisites. * +0 WARN or invalid execution context. The patch establishes signal delivery with interrupts disabled, but does not demonstrate a panic, memory corruption, or persistent system stall. Paranoid difference: * +1 Strong DoS concern. On PREEMPT_RT, entering signal-delivery locking or scheduling paths with interrupts disabled can plausibly stall the kernel. This remains an availability-only interpretation. Not awarded: * No UAF, OOB access, stale object, repeated release, or refcount corruption exists. * No reliable kernel crash is directly demonstrated. * No confidentiality or integrity impact is established. * No arbitrary write, controlled reclaim, privilege escalation, or security-boundary bypass exists. * No remote reachability exists. * No extra availability point was awarded for the same possible stall. 3. Reachability analysis An ordinary local user can execute the faulting instruction, so host-admin privilege is not required. No capability or namespace privilege participates in the trigger. The complete path is local code execution followed by an unhandled user fault and `force_sig_fault()`. The vulnerable environment must already be a 32-bit ARM PREEMPT_RT kernel built with `CONFIG_PERF_EVENTS=n`. These are administrator-controlled build and boot prerequisites, but no separate privileged actor must configure a runtime object for each attack. There is no race, special timing window, network path, or external hardware input requirement beyond the ARM platform itself. 4. Primitive and severity interpretation The exact defect is an interrupt-state handling error. `do_DataAbort()` and `do_PrefetchAbort()` can call the signal-delivery path with local interrupts disabled after a fault handler returns an error. This is CLASS_C invalid-state and potential DoS behavior. It is not a lifetime violation or memory-corruption primitive. The demonstrated consequence is an invalid PREEMPT_RT execution context. A warning, scheduling failure, locking failure, or stall is plausible, while a host-wide crash is not directly shown. ImportantCandidate is NO because there is no exploitation leverage beyond availability impact. AutoDowngradeAllowed is YES because no unresolved corruption, ownership, authorization, or security-boundary primitive remains. Likely operational severity is Low to ordinary Moderate and limited to the affected kernel configuration. 5. One-sentence report phrase An unprivileged local process can trigger signal delivery with interrupts disabled on affected 32-bit ARM PREEMPT_RT kernels, potentially causing a warning or availability failure without memory corruption or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a configuration-specific local availability bug with no established memory-corruption or security-boundary primitive. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ARM: 9484/1: enable interrupts when unhandled user faults are triggered [ Upstream Commit: 8d7cbc6df9632d334b21c4be66ccdde76a08fb13 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d7cbc6df9632d334b21c4be66ccdde76a08fb13 Changed files: arch/arm/mm/fault.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=8d7cbc6df9632d334b21c4be66ccdde76a08fb13 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90304 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90304 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:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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).