From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74713][MODERATE REGULAR] vhost_iotlb: bound map allocation in add_range [ Upstream Date: Sat, 22 Aug 2026 12:54:57 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74713 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 4 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: ae128dd19040ee06a4f8143c7ced4d18080d7a9a List-Id: CVE: CVE-2026-74713 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: vhost_iotlb: bound map allocation in add_range [ Upstream Commit: ae128dd19040ee06a4f8143c7ced4d18080d7a9a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae128dd19040ee06a4f8143c7ced4d18080d7a9a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74713 Analysis date: Sat, 22 Aug 2026 12:54:57 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Ordinary Moderate / Borderline resource-exhaustion issue, not an Important candidate Manual review required: NO Summary: A vhost IOTLB limit handling flaw allowed non-retiring or zero-limit IOTLB tables to keep allocating map entries beyond intended bounds, enabling local or guest-mediated kernel memory exhaustion and host denial of service. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74713 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74713 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 REGULAR 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-2026-74713 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-770;**CWE-400;CWE-459;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'vhost IOTLB tables could keep allocating map entries beyond the configured limit when the table did not use retire mode or when callers created zero limit tables that could still be populated. This can allow a local vhost or vdpa control process, or a guest controlled request path in affected deployments, to consume kernel memory and cause denial of service on the host. For the CVSS the PR:L is used in the paranoid score because reliable triggering requires access to a local vhost vdpa VDUSE interface or a guest controlled path exposed by the host, but it does not require full host administrator privileges in all practical deployments. The issue is not directly Internet reachable. Impact is resource exhaustion and host availability loss only. There is no concrete evidence of UAF, OOB access, information disclosure, or privilege escalation in this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Borderline resource-exhaustion issue, not an Important candidate (with actual score 4) YES OOB INIT NOMEMCHK HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Ordinary Moderate / Borderline resource-exhaustion issue, not an Important candidate** ## 2. Signal breakdown Conservative signals: * Local unprivileged or reduced-privilege trigger: +1 Triggering may be possible from a local vhost/vDPA/VDUSE control process or from a guest-controlled request path in some deployments, but not from the network directly. * Reliable kernel resource exhaustion / DoS concern: +1 Non-retiring IOTLB tables could allocate entries beyond their intended limit, allowing sustained kernel memory growth. * Availability impact realistic: +1 Sustained abuse can plausibly consume kernel memory and affect host availability. Paranoid additional signal: * Cross-boundary isolation/resource impact: +1 In virtualization or vDPA deployments, guest-influenced IOTLB updates may consume host kernel memory, so this can affect isolation expectations between guest or delegated device users and the host. Not awarded: * No generic memory corruption bonus. The patch does not show UAF, double free, OOB write, type confusion, refcount takeover, or arbitrary write. * No privilege escalation bonus. The demonstrated primitive is resource exhaustion only. * No confidentiality or integrity impact. There is no supported leak or unauthorized write primitive. * No remote/network-triggerable bonus. The path is local or virtualization/device-control mediated, not Internet-facing protocol parsing. ## 3. Reachability analysis The affected path is in vhost IOTLB handling and related vDPA, VDUSE, vdpa_sim, and mlx5 vDPA users. A trigger generally requires access to a vhost/vDPA/VDUSE interface, a management process such as a hypervisor, or a guest-controlled IOTLB update path exposed by the host configuration. This is not directly reachable over the network. Namespaces and containers can matter if device nodes or vhost/vDPA management capabilities are delegated, but typical deployments still require a local process or guest context with access to the relevant virtualization or device interface. The affected components are important in virtualization and device passthrough contexts, but not universally enabled for untrusted users by default. Call-site confidence: high. The patch includes the common helper and several caller-side users that previously allocated zero-limit IOTLB tables or failed to enforce usable limits. ## 4. Severity interpretation This behaves like an ordinary Moderate to borderline actionable resource-exhaustion issue, not an Important-class kernel vulnerability. The practical impact is host memory pressure or denial of service through unbounded IOTLB map allocation. The patch also fixes partial full-range mapping insertion, but the evidence still points to consistency and resource-bound enforcement rather than memory corruption. Theoretical escalation beyond DoS is not supported by the patch. There is no concrete primitive for UAF, stale pointer reuse, arbitrary overwrite, page-cache corruption, or sensitive data exposure. ## 5. One-sentence report phrase A vhost IOTLB limit handling flaw allowed non-retiring or zero-limit IOTLB tables to keep allocating map entries beyond intended bounds, enabling local or guest-mediated kernel memory exhaustion and host denial of service. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This is a resource-exhaustion issue without evidence of memory corruption, privilege escalation, confidentiality impact, or direct network reachability. Manual environment review may be useful only for deployments that expose vhost-vDPA or VDUSE interfaces to untrusted tenants. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: vhost_iotlb: bound map allocation in add_range [ Upstream Commit: ae128dd19040ee06a4f8143c7ced4d18080d7a9a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ae128dd19040ee06a4f8143c7ced4d18080d7a9a Changed files: drivers/vdpa/mlx5/core/mlx5_vdpa.h drivers/vdpa/mlx5/core/mr.c drivers/vdpa/mlx5/core/resources.c drivers/vdpa/vdpa_sim/vdpa_sim.c drivers/vdpa/vdpa_user/iova_domain.c drivers/vhost/iotlb.c drivers/vhost/vdpa.c drivers/vhost/vhost.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=ae128dd19040ee06a4f8143c7ced4d18080d7a9a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74713 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74713 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:L/PR:L/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 4 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 REGULAR 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).