From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-90430][LOW] iommu/tegra241-cmdqv: Publish an LVCMDQ only after it is fully initialized [ Upstream Date: Thu, 17 Sep 2026 12:55:54 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-90430 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: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: 792f720fc23fe5bd6508d40ed73ae739debd6dcb List-Id: CVE: CVE-2026-90430 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: iommu/tegra241-cmdqv: Publish an LVCMDQ only after it is fully initialized [ Upstream Commit: 792f720fc23fe5bd6508d40ed73ae739debd6dcb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=792f720fc23fe5bd6508d40ed73ae739debd6dcb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90430 Analysis date: Thu, 17 Sep 2026 12:55:54 -0400 ActionableScore: 2 ActionableScore lower bound: 1 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-2026-90430 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90430 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-2026-90430 LOW https://www.kernelcve.org/list/?q=CVE-2026-90430 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:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-665;**CWE-476;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'The Tegra241 CMDQV driver can expose an LVCMDQ pointer to the VINTF0 error ISR before the embedded arm_smmu_cmdq is fully initialized. If a latched LVCMDQ error fires in this narrow initialization window, for example after kexec or device recovery, the ISR may pass a zeroed command queue into __arm_smmu_cmdq_skip_err and dereference NULL queue register pointers. For the CVSS the PR:L is used for the paranoid score because delegated device or IOMMU management could make a local non root service account relevant in some deployments, while the typical base case is closer to PR:H. The issue is not network reachable and requires local system context plus specific Tegra241 CMDQV hardware state. Impact is denial of service via kernel crash. No confidentiality or integrity impact is assigned because the observed primitive is a NULL pointer dereference rather than UAF, OOB access, or controllable memory corruption.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES INIT SIMPLEFIX LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate**:: No floor or cap changed the score. 2. Signal breakdown Conservative signals: * +1 Weak indirect corruption candidate. A partially initialized `vcmdq` pointer can be observed by the VINTF0 error ISR before `vcmdq->cmdq` is fully built. * +1 Reliable kernel crash / strong DoS. The ISR can pass a zeroed `arm_smmu_cmdq` into `__arm_smmu_cmdq_skip_err()`, leading to NULL queue register pointer dereference. * -1 Hard timing / narrow window. The error must fire during the small publication-before-initialization window. * 0 Hardware specificity noted but not additionally subtracted in conservative arithmetic to avoid over-penalizing beyond the narrow timing condition. Paranoid signals: * +1 Weak indirect corruption candidate. Same partially initialized active object exposure. * +1 Reliable kernel crash / strong DoS. Same NULL dereference host crash path. * 0 No timing penalty in paranoid score because a latched error inherited across kexec could make the ordering less purely probabilistic once the affected hardware state exists. Important non-awarded signals: * Real UAF not awarded. The patch shows premature publication of an incompletely initialized object, not post-free use. * Controlled reclaim not demonstrated. * Arbitrary or directed write not demonstrated. * Confidentiality and integrity impact not awarded. * Remote reachability not established. * Concrete repeated release/refcount mutation not established. * Structured stale-object exploitation leverage not awarded because the stale operation is a NULL dereference path, not meaningful post-reuse structured consumption. * Extra availability point not awarded because the same kernel crash is already counted once. 3. Reachability analysis The affected path is in the NVIDIA Tegra241 Grace CMDQV IOMMU driver. The vulnerable reader is the VINTF0 error ISR, which can walk `vintf->lvcmdqs[]` while allocation is still in progress. The clearest trigger condition is a latched LVCMDQ error, for example one inherited across kexec, firing during initialization. kexec and low-level IOMMU or device recovery are normally host-admin-level operations, but the supplied evidence does not fully prove that every possible trigger requires host admin. Therefore `HostAdminRequired=UNKNOWN` rather than YES. No namespace-scoped capability path is shown. The operation is hardware and driver initialization/error handling, not a namespace-local object. `NamespaceScopedPrivilege=NO`. No direct network trigger is shown. No ordinary local unprivileged trigger is established. Special Tegra241 CMDQV hardware is required, but the main reduction is the narrow ISR/init ordering rather than a separate rare-hardware penalty. 4. Primitive and severity interpretation The exact primitive is premature publication of an incompletely initialized `struct tegra241_vcmdq` into `vintf->lvcmdqs[]`, allowing a lockless ISR reader to observe it before the embedded `arm_smmu_cmdq` is valid. This is an initialization-order race / synchronization bug with a NULL pointer dereference consequence. It is not a UAF, not a double release, and not an OOB access. The demonstrated consequence is kernel crash / DoS. Stronger exploitation is not supported because there is no controlled replacement object, no attacker-shaped post-free data, no callback control, no arbitrary read/write, and no authorization boundary bypass. PrimitiveClass is CLASS_C because the demonstrated behavior is primarily invalid-state crash behavior without an independently useful corruption primitive. ImportantCandidate is NO because the patch supports DoS-only impact and does not establish meaningful unresolved memory-corruption leverage. AutoDowngradeAllowed is YES because this is a constrained hardware-specific crash path with no demonstrated UAF, repeated lifetime mutation, security-boundary bypass, or controlled corruption. 5. One-sentence report phrase The Tegra241 CMDQV driver could expose an LVCMDQ to the error ISR before full initialization, allowing a latched hardware error during a narrow initialization window to trigger a NULL pointer dereference and kernel crash. 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: this is a constrained initialization-order NULL dereference on specific Tegra241 CMDQV hardware, with no UAF, no repeated refcount mutation, no C/I primitive, and no established non-admin or remote trigger. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iommu/tegra241-cmdqv: Publish an LVCMDQ only after it is fully initialized [ Upstream Commit: 792f720fc23fe5bd6508d40ed73ae739debd6dcb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=792f720fc23fe5bd6508d40ed73ae739debd6dcb Changed files: drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.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=792f720fc23fe5bd6508d40ed73ae739debd6dcb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-90430 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90430 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:H 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: 1 Paranoid ActionableScore: 2 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).