From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64476][LOW] vfio/pci: Latch disable_idle_d3 per device [ Upstream Date: Sat, 25 Jul 2026 10:55:50 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64476 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: 332d785f9ae426eeeb92527872adf09d84101ba3 List-Id: CVE: CVE-2026-64476 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: vfio/pci: Latch disable_idle_d3 per device [ Upstream Commit: 332d785f9ae426eeeb92527872adf09d84101ba3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=332d785f9ae426eeeb92527872adf09d84101ba3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64476 Analysis date: Sat, 25 Jul 2026 10:55:50 -0400 ActionableScore: 1 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: vfio-pci could use a mutable global disable_idle_d3 value for already initialized devices, causing unbalanced runtime PM operations and possible local VFIO device availability degradation, but no memory corruption or privilege escalation primitive is evident. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64476 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64476 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-2026-64476 LOW 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-664;CWE-665;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'vfio/pci could use a mutable global disable_idle_d3 value for devices that were already initialized, while runtime PM requires balanced get and put operations. If the module parameter or vfio-pci module state changes relative to an existing bound device, later enable disable unregister or reset paths may perform mismatched PM operations and leave the device runtime PM state inconsistent. For the CVSS the PR:L is used in the paranoid interpretation because VFIO device access is sometimes delegated to a VM process or service account even when full module management is administrative. The issue is not network reachable and requires local interaction with VFIO PCI device management paths. Impact is denial of service or device availability degradation only. There is no evidence of UAF, out of bounds access, information disclosure, or privilege escalation in this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) YES DANGER HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Triggered signals: * Availability impact realistic: +1 The bug can leave runtime PM get and put operations unbalanced, which may cause device power-management inconsistency, failed reset behavior, device unavailability, or VFIO workload disruption. * Requires admin/root/CAP in typical deployments: -2 Reliable setup appears to require vfio-pci module loading, unloading, parameter changes, PCI device binding, or VFIO device-management operations, which are normally administrator-controlled. * Rare or configuration-dependent exposure: -1 The affected path requires VFIO PCI usage, runtime PM behavior, and non-default or changed disable_idle_d3 state relative to already bound devices. Paranoid adjustment: * Delegated VFIO operation concern: +1 In some virtualization deployments, a reduced-privilege service account or VM management process may be allowed to operate VFIO devices or trigger reset paths after the inconsistent state exists. This does not make the issue a privilege-escalation candidate, but it prevents treating it as purely irrelevant. Not triggered: * No remote/network reachability. * No firmware-mediated attacker influence shown. * No UAF, double-free, OOB write, type confusion, arbitrary write, or page-cache corruption. * No confidentiality or integrity impact supported. * No practical LPE path supported. * No reliable host-wide kernel crash is described. Call-site confidence: high. The patch shows the affected enable, disable, register, unregister, and reset paths. ## 3. Reachability analysis The bug is local and tied to VFIO PCI device-management paths. In typical deployments, changing the module parameter, reloading vfio-pci, binding PCI devices, or controlling VFIO device reset behavior requires administrative privileges or a privileged virtualization stack. Namespaces do not generally make VFIO PCI management unprivileged, although a VM service account may have delegated access to already configured VFIO devices. The path is not default-exposed to remote attackers and is not packet-triggerable. ## 4. Severity interpretation This behaves like a low-end Moderate or Low-like operational DoS issue rather than an Important kernel vulnerability. The bug is a runtime PM state-consistency problem, not a memory lifetime or memory corruption primitive. The realistic impact is device availability degradation or reset/power-management failure. Theoretical escalation is not supported by the patch because the affected state is a PM usage-count decision, not attacker-controlled memory, credentials, file descriptors, page ownership, or callback state. ## 5. One-sentence report phrase vfio-pci could use a mutable global disable_idle_d3 value for already initialized devices, causing unbalanced runtime PM operations and possible local VFIO device availability degradation, but no memory corruption or privilege escalation primitive is evident. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue can be handled as an ordinary low-priority VFIO runtime PM correctness fix unless product-specific deployment gives untrusted users delegated VFIO reset or module-management capabilities. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: vfio/pci: Latch disable_idle_d3 per device [ Upstream Commit: 332d785f9ae426eeeb92527872adf09d84101ba3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=332d785f9ae426eeeb92527872adf09d84101ba3 Changed files: drivers/vfio/pci/vfio_pci_core.c include/linux/vfio_pci_core.h 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=332d785f9ae426eeeb92527872adf09d84101ba3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64476 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64476 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:L 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: 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).