[CVE-2026-74713][MODERATE REGULAR] vhost_iotlb: bound map allocation in add_range [ Upstream

[CVE-2026-74713][MODERATE REGULAR] vhost_iotlb: bound map allocation in add_range [ Upstream

[AL-KERNEL]

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.

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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

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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).