From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53322][IMPORTANT] vfio/pci: Clean up DMABUFs before disabling function [ Upstream Date: Fri, 26 Jun 2026 16:04:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53322 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 7 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 4f1000a30f67cf7d328059242776a858611d5ef9 List-Id: CVE: CVE-2026-53322 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: vfio/pci: Clean up DMABUFs before disabling function [ Upstream Commit: 4f1000a30f67cf7d328059242776a858611d5ef9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4f1000a30f67cf7d328059242776a858611d5ef9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53322 Analysis date: Fri, 26 Jun 2026 16:04:17 -0400 ActionableScore: 7 ActionableScore lower bound: 5 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: VFIO PCI could leave a stale DMABUF mapping to MMIO BAR resources during device shutdown, allowing local VFIO users to retain unintended access after function disable and possible BAR reuse by another driver. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53322 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53322 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: IMPORTANT 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-2026-53322 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-672;CWE-362;CWE-284;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'VFIO PCI DMABUF cleanup was performed after vfio_pci_core_disable, leaving a small shutdown window where MMIO BAR access through exported DMABUFs could remain possible after the function MSE was cleared. If the BAR resources are freed and later claimed by another driver, a stale DMABUF mapping may expose unintended MMIO access to resources that should no longer belong to the VFIO user. For the CVSS the PR:L is used because exploitation requires local access to an assigned VFIO PCI device or a process that can hold exported DMABUFs, not full host administrator privileges. The issue is not network reachable and is triggered through local VFIO device lifecycle operations. Impact is at least local denial of service or device state corruption, and in the paranoid case may include confidentiality and integrity impact through stale MMIO access to reused BAR resources. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) SKIP CVE-2026-53322 SKIP The Fixes patch not applied yet, so unlikely that actual: 5d74781ebc86c5fa9e9d6934024c505412de9b52 YES NO NO unknown MAYBE UAF HARDWARE KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: 5 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local low-privileged trigger: +1. A user or process with access to an assigned VFIO PCI device and exported DMABUFs can participate in the vulnerable lifecycle path. * Real lifetime corruption: +1. DMABUF access can outlive the expected BAR accessibility window during device shutdown. * Privileged kernel/device-management resource lifetime path: +1. The bug is in VFIO PCI teardown and BAR/MMIO resource management. * Confidentiality impact plausible: +1. Stale MMIO access could expose resources after ownership changes. * Integrity impact plausible: +1. Stale MMIO access could potentially modify device/MMIO state that no longer belongs to the VFIO user. * Hard or tiny timing window: -1. The commit explicitly describes a tiny window. * Rare/configuration-dependent exposure: -1. Requires VFIO PCI DMABUF export support and a suitable device assignment setup. * Cross-boundary resource ownership concern: +1. The stale mapping may cross from an old VFIO user into resources later claimed by another driver. Paranoid additional interpretation: * Security-boundary bypass with sensitive resource access: +2 instead of only +1 cross-boundary concern. If BAR resources are freed and reused by another driver while a stale DMABUF mapping still allows access, this becomes a meaningful VFIO/device isolation bypass. * Availability impact realistic: +1. Incorrect MMIO access after teardown or reuse can plausibly cause device malfunction or host-impacting device errors. ## 3. Reachability analysis The bug is local, not network reachable. It requires VFIO PCI usage with DMABUF export support for MMIO regions. The attacker normally needs access to an assigned VFIO device or a process that can hold exported DMABUFs, so this is not full host-root by itself and should not be reduced to PR:H automatically. Namespaces and containers may matter if VFIO device access is delegated to a VM manager, container, sandboxed service, or reduced-capability root process. In typical deployments, initial device assignment is administrative, but the vulnerable close/teardown window may be reachable by the less-privileged consumer that already owns the VFIO device fd or DMABUF. Realistic exploitation depends on precise teardown timing and whether BAR resources are quickly reused by another driver. This makes exploitation less straightforward, but the resource lifetime and isolation implications are strong enough for manual review. ## 4. Severity interpretation This is not ordinary generic kernel memory corruption. It is a stale device MMIO resource lifetime bug in a privileged VFIO PCI path. The realistic impact is at least Actionable Moderate because stale DMABUF access after function disable can violate expected revocation of MMIO access. The paranoid interpretation reaches Strong Important candidate because the commit explicitly states that BAR resources may be freed and become available to another driver while DMABUF access may still exist. That creates a plausible confidentiality and integrity boundary issue across device ownership, even without a demonstrated arbitrary write or kernel-code-execution primitive. ## 5. One-sentence report phrase VFIO PCI could leave a stale DMABUF mapping to MMIO BAR resources during device shutdown, allowing local VFIO users to retain unintended access after function disable and possible BAR reuse by another driver. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a local VFIO/device resource lifetime and isolation issue with plausible stale MMIO access across ownership changes. The tiny race window reduces reliability, but the potential boundary bypass and C/I impact make auto-closure unsafe. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: vfio/pci: Clean up DMABUFs before disabling function [ Upstream Commit: 4f1000a30f67cf7d328059242776a858611d5ef9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4f1000a30f67cf7d328059242776a858611d5ef9 Changed files: drivers/vfio/pci/vfio_pci_core.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=4f1000a30f67cf7d328059242776a858611d5ef9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53322 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53322 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:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 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: 5 Paranoid ActionableScore: 7 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).