[CVE-2026-64319][MODERATE 7.0] nvmet-auth: validate reply message payload bounds against transfer length [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-64319
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: nvmet-auth: validate reply message payload bounds against transfer length [ Upstream
Commit: 80cd28b56ab62d3e7ed0a7bf05282e6d3ee5b2a0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80cd28b56ab62d3e7ed0a7bf05282e6d3ee5b2a0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64319
Analysis date: Sat, 25 Jul 2026 13:10:56 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A pre-authentication out-of-bounds heap read in NVMe-oF target DHCHAP reply handling allows a malicious initiator with storage-network access to send malformed `hl` and `dhvlen` values and potentially crash the kernel or expose adjacent heap data.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-64319 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64319

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-64319	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H';CWE-125;CWE-130;*CWE-20;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '8.1';DESCR 'An out-of-bounds heap read in the NVMe-oF target authentication path occurs because nvmet_auth_reply() uses attacker-controlled hl and dhvlen fields from DHCHAP_REPLY before proving that the variable length rval data fits inside the received transfer length. A malicious initiator can send a small payload with large hl or dhvlen values and make the target read past the allocated buffer while processing the DH public key or comparing the host response. With DH authentication configured, the out-of-bounds pointer can be passed to sg_init_one() and then consumed by crypto_kpp_compute_shared_secret(), reaching beyond the attacker supplied buffer before authentication completes. For the CVSS the PR:N value is used because the vulnerable path is reachable by an unauthenticated NVMe-oF initiator that can connect to the target listener. The issue is adjacent-network reachable rather than Internet-wide in typical deployments, because NVMe-oF targets are usually exposed only on isolated storage or data-center networks. Impact is at least denial of service and may include confidentiality impact from heap over-read, but the patch does not show an arbitrary write primitive or a direct integrity bypass.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	WRITE OOB SIMPLEFIX NVME LINUS KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	YES	NO	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2
  NVMe-oF target authentication is reachable by an initiator over the storage network before authentication completes.
* Reliable kernel crash / strong DoS: +1
  The target can perform out-of-bounds heap reads through `sg_init_one()` and `crypto_kpp_compute_shared_secret()`, which can plausibly crash the kernel or destabilize the target.
* Confidentiality impact plausible: +1
  This is an OOB heap read in an authentication path. No direct disclosure channel is shown, but heap over-read can expose adjacent kernel data to crypto/auth processing.
* Important filesystem/storage path: +1
  The affected code is in NVMe-oF target authentication, a security-sensitive storage access path.
* Practical exploit chain strongly implied: +1
  The commit describes a concrete pre-auth trigger: small transfer length plus large `hl` or `dhvlen` in `DHCHAP_REPLY`.
* Rare/config-dependent exposure: -1 conservative only
  Requires NVMe-oF target with DHCHAP authentication configured and reachable from the attacker.

Conservative total: 5.
Paranoid total: 6 by not applying the exposure reduction because the bug is pre-auth and directly network-triggerable in affected NVMe-oF deployments.

## 3. Reachability analysis

An unauthenticated NVMe-oF initiator that can connect to the target listener can trigger the bug by sending a malformed `DHCHAP_REPLY`. No local user account on the target is required. This is not usually Internet-wide exposure because NVMe-oF targets are normally deployed inside storage, data-center, or trusted internal networks. Namespaces and containers are not the main gating factor here. The practical prerequisite is network reachability to an NVMe-oF target with DH authentication enabled.

## 4. Severity interpretation

This is more than an ordinary Moderate issue because it is pre-authentication, network-reachable in affected storage deployments, and involves a concrete OOB heap read primitive. It does not show an OOB write, arbitrary write, UAF reclaim, or direct privilege escalation path, so Important classification should be based on strong DoS plus plausible confidentiality impact rather than assumed code execution. The conservative result is Actionable Moderate. The paranoid result is a Strong Important candidate for manual review.

## 5. One-sentence report phrase

A pre-authentication out-of-bounds heap read in NVMe-oF target DHCHAP reply handling allows a malicious initiator with storage-network access to send malformed `hl` and `dhvlen` values and potentially crash the kernel or expose adjacent heap data.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.
YES REQUIRES MANUAL CHECK because this is a pre-auth network-reachable OOB heap read in a storage authentication path, with plausible DoS and confidentiality impact even though no write primitive or direct LPE path is shown.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: nvmet-auth: validate reply message payload bounds against transfer length [ Upstream
Commit: 80cd28b56ab62d3e7ed0a7bf05282e6d3ee5b2a0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80cd28b56ab62d3e7ed0a7bf05282e6d3ee5b2a0

Changed files:
  drivers/nvme/target/fabrics-cmd-auth.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=80cd28b56ab62d3e7ed0a7bf05282e6d3ee5b2a0

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-64319 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64319

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:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
  The Best / paranoid CVSS score: 8.1

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: 6

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: YES
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).