From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45944][MODERATE 7.0] iommu/vt-d: Clear Present bit before tearing down context entry [ Upstream Date: Wed, 27 May 2026 09:27:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45944 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: d2138abc8f0a7fce4101b7229b43b06811ed083d List-Id: CVE: CVE-2026-45944 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: iommu/vt-d: Clear Present bit before tearing down context entry [ Upstream Commit: d2138abc8f0a7fce4101b7229b43b06811ed083d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d2138abc8f0a7fce4101b7229b43b06811ed083d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45944 Analysis date: Wed, 27 May 2026 09:27:55 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45944 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45944 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-2026-45944 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H';CWE-362;CWE-667;CWE-693;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'Intel VT-d context entry teardown can expose a torn DMA remapping context to hardware because the 128 bit entry is cleared with multiple writes while the Present bit may still be visible. This can cause spurious IOMMU faults or unpredictable device behavior, and in the paranoid interpretation it may affect DMA isolation because hardware could transiently consume an inconsistent but still Present context entry. For the CVSS the PR:H is used because reliable triggering normally requires privileged device management such as domain teardown, PASID setup, driver unload, hotplug, or similar host control. The issue is not network reachable and is not a normal local user syscall path. Impact is primarily availability, but confidentiality and integrity are kept high in the paranoid score because the affected object is an IOMMU translation context and the bug touches the DMA isolation boundary.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES INIT DMAorINTERRUPT HARDWARE MEMORY DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO YES checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: 2. Signal breakdown * Privileged kernel/device-management path: +1. The affected code is Intel VT-d context teardown and PASID/context setup, which is a trusted DMA-remapping path. * Security-boundary / DMA isolation concern: +1 paranoid. The bug touches IOMMU context entries, so a torn valid entry may transiently affect the DMA isolation boundary. * Reliable availability impact: +1. The commit explicitly mentions unpredictable behavior and spurious faults from hardware consuming a torn Present entry. * Confidentiality impact plausible: +1 paranoid. Not demonstrated, but an inconsistent DMA remapping context can defensibly raise concern about device access to unintended memory. * Integrity impact plausible: +1 paranoid. Same reason: DMA isolation inconsistencies may theoretically allow unintended DMA writes or corruption, though no concrete primitive is shown. * Broad/default subsystem exposure: +1. Intel VT-d/IOMMU is common on many x86 systems, especially virtualization and device-isolation deployments. * Requires admin/root/device-management privileges: -2. Reliable triggering normally requires domain teardown, PASID setup, driver unload, hotplug, device assignment, or similar privileged host control. * No direct memory corruption primitive: +0. The patch does not show UAF, OOB write, arbitrary write, or controlled overwrite by userspace. * No remote reachability: +0. This is not network-triggered. 3. Reachability analysis The issue is reachable during Intel VT-d context entry teardown or replacement, including device domain teardown, PASID setup, driver unload, hotplug, or device-management transitions. In normal deployments these operations require host administrative privileges or privileged virtualization/device assignment control. Containers and user namespaces generally do not lower the requirement unless they are delegated real device-management authority. The path is not reachable by ordinary packet traffic or a normal unprivileged syscall. 4. Severity interpretation This is not a proven privilege escalation bug, and the realistic observed impact is likely DoS via IOMMU faults or device malfunction. However, it is more actionable than an ordinary Moderate because the affected object is an IOMMU DMA-remapping context and the bug violates the VT-d ownership/invalidation handshake. The theoretical risk is DMA isolation inconsistency. The realistic evidence does not prove controlled memory access, but the boundary involved justifies manual triage. 5. One-sentence report phrase Intel VT-d context teardown could expose a torn Present context entry to hardware, potentially causing IOMMU faults or transient DMA-remapping inconsistency during privileged device-management operations. 6. Manual review recommendation MANUAL CHECK REQUIRED The issue affects IOMMU context ownership and DMA isolation semantics. Even though exploitation appears privileged and no concrete arbitrary DMA primitive is shown, IOMMU boundary bugs should not be auto-closed without review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: iommu/vt-d: Clear Present bit before tearing down context entry [ Upstream Commit: d2138abc8f0a7fce4101b7229b43b06811ed083d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d2138abc8f0a7fce4101b7229b43b06811ed083d Changed files: drivers/iommu/intel/iommu.c drivers/iommu/intel/iommu.h drivers/iommu/intel/pasid.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=d2138abc8f0a7fce4101b7229b43b06811ed083d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45944 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45944 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:H/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 6.4 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: 3 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: NO 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).