From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80895][MODERATE 7.0] mshv: Order pt_vp_array publish against irqfd assertion path [ Upstream Date: Fri, 04 Sep 2026 15:25:42 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80895 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: 062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 List-Id: CVE: CVE-2026-80895 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: mshv: Order pt_vp_array publish against irqfd assertion path [ Upstream Commit: 062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80895 Analysis date: Fri, 04 Sep 2026 15:25:42 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: A local mshv user can race irqfd assertion with VP creation so the irqfd fast path observes a non NULL VP pointer before initialization is fully visible, which may cause incorrect hypervisor state use or host kernel DoS on weakly ordered architectures. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80895 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80895 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-80895 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80895 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-362;CWE-667;CWE-665;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in the mshv irqfd fast path can allow mshv_try_assert_irq_fast() to observe a non NULL VP pointer while mshv_partition_ioctl_create_vp() is still publishing the newly initialized VP state. On weakly-ordered architectures this can expose partially initialized fields such as vp_register_page to a lockless reader and may cause incorrect interrupt delivery, VMM failure, or a host kernel denial of service. For the CVSS the PR:L value is used because triggering requires local access to /dev/mshv and the ability to create VP and irqfd state, but this may be available to a VMM process or a reduced capability service account rather than full host administrator access. The issue is not network reachable and is triggered through local mshv device operations. Impact is at least local denial of service. In the worst still-defensible case it may allow limited confidentiality or integrity impact because a partially initialized kernel object is consumed in a hypervisor fast path, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES INIT RACE HARDWARE INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP YES NO 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 Conservative signals: * Local trigger: +1. Triggering requires local access to `/dev/mshv` and the ability to create VP and irqfd state. * Weak or indirect corruption candidate: +1. The reader can observe a non NULL VP pointer before initialization stores are visible, causing use of a partially initialized kernel object. * Reliable kernel crash or strong DoS concern: +1. Use of fields such as `vp_register_page` before visible initialization can plausibly cause VMM failure or host kernel DoS. * Hard race or special timing required: -1. The bug requires concurrent `MSHV_IRQFD` assertion and `MSHV_CREATE_VP`. * Rare or configuration dependent subsystem: +0. `mshv` is not a broad default subsystem, but it is reachable through an ordinary local device interface when enabled. Paranoid additional signals: * Privileged kernel or hypervisor device-management path: +1. The affected object is a VP in a hypervisor-facing kernel driver path. * Confidentiality impact plausible: +1. Limited C impact is defensible only as a worst-case concern from consuming partially initialized hypervisor state. * Integrity impact plausible: +1. Limited I impact is defensible only as a worst-case concern from incorrect interrupt delivery or corrupted VP state use. * No strong LPE signal awarded. The patch does not show UAF reclaim, object replacement, write-after-free, callback control, type confusion, refcount takeover, or arbitrary write. ## 3. Reachability analysis The bug is locally reachable by a process that can access `/dev/mshv` and create both irqfd and VP state. This is not a network reachable path. The realistic attacker is a VMM process, service account, reduced capability root, or another local actor delegated access to the MSHV interface. Full host root should not automatically be assumed because VMM service accounts may be capability separated. The race is structurally plausible because `MSHV_IRQFD` does not require the target `lapic_apic_id` to already refer to an existing VP. A user can register an irqfd for a not yet created VP and then race eventfd wakeup against `MSHV_CREATE_VP`. The issue is mainly relevant on weakly ordered architectures. On x86 TSO the acquire and release operations compile to plain accesses, which lowers practical exposure there. ## 4. Severity interpretation This behaves more like an Actionable Moderate than ordinary Low or auto-close Moderate. The demonstrated primitive is a memory ordering race leading to consumption of a partially initialized kernel object, not a confirmed UAF or arbitrary write. Realistic impact is local DoS or VMM failure. The paranoid score reaches 5 because the object is consumed in a hypervisor fast path and limited confidentiality or integrity impact cannot be fully excluded without deeper source review. It is not a Strong Important candidate from the supplied patch alone because the destroy-side lifetime issue is explicitly out of scope and the patch does not demonstrate attacker-controlled reclaim, stale object reuse, write primitive, or privilege escalation. ## 5. One-sentence report phrase A local mshv user can race irqfd assertion with VP creation so the irqfd fast path observes a non NULL VP pointer before initialization is fully visible, which may cause incorrect hypervisor state use or host kernel DoS on weakly ordered architectures. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: this is a race and memory ordering bug in a hypervisor device path. The current evidence supports DoS and limited worst-case C/I concern, but not confirmed privilege escalation or strong memory corruption. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: mshv: Order pt_vp_array publish against irqfd assertion path [ Upstream Commit: 062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 Changed files: drivers/hv/mshv_eventfd.c drivers/hv/mshv_root_main.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=062aa5dcc49a9ad96726a80c2a0ab0a1233bc2b9 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80895 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80895 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:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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).