[CVE-2026-80791][MODERATE 7.0] nvmet-auth: zero the AUTH_RECEIVE response buffer

[CVE-2026-80791][MODERATE 7.0] nvmet-auth: zero the AUTH_RECEIVE response buffer

[AL-KERNEL]

CVE: CVE-2026-80791
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: nvmet-auth: zero the AUTH_RECEIVE response buffer
Commit: 447b668faa14710f611e714031e3739ac3ec3a4f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=447b668faa14710f611e714031e3739ac3ec3a4f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80791
Analysis date: Fri, 04 Sep 2026 17:06:51 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80791 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80791

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-2026-80791	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80791 CHECK WITH IMPACT FROM ORIG NN MODERATE	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:N';*CWE-200;CWE-908;CWE-201;BEST CVSS score: '6.5';DESCR 'An information disclosure flaw exists in the NVMe/TCP target authentication path because nvmet_execute_auth_receive allocates the AUTH_RECEIVE response buffer with kmalloc using a host supplied allocation length. The DH-HMAC-CHAP response builders write only the actual fixed size authentication message, but the full allocation length is later copied back to the initiator. A remote initiator can therefore receive uninitialized kernel slab bytes past the valid response during the pre-authentication handshake, potentially up to nearly one page per request. For the CVSS the PR:N is used because the issue can be reached before successful authentication and does not require privileges beyond access to the exposed NVMe target endpoint. AV:A is used because NVMe/TCP targets are typically deployed on isolated storage or data center networks rather than the public Internet. Impact is confidentiality loss through kernel memory disclosure. No direct integrity or availability impact is indicated by the code path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	SIMPLEFIX NVME LINUS  INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

1. ActionableScore
* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Remote reachable / network-triggerable: +2. The vulnerable AUTH_RECEIVE path is reachable by an NVMe initiator over an exposed NVMe Fabrics target endpoint.
* Confidentiality impact plausible: +1. The bug leaks uninitialized kernel slab bytes to the initiator.
* Important filesystem/storage path: +1. The issue is in the NVMe target storage stack and affects authentication handling.
* Security-boundary bypass with practical sensitive-object access: +1 in paranoid scoring. The leak occurs during the pre-authentication handshake, so an unauthenticated initiator can receive kernel memory contents before successful authentication.
* No memory corruption score. The patch changes kmalloc to kzalloc and indicates information disclosure, not UAF, OOB write, overwrite, or object lifetime corruption.
* No integrity or availability score. The described primitive is disclosure of uninitialized memory only.

3. Reachability analysis
A remote NVMe initiator can trigger the issue by sending AUTH_RECEIVE with an allocation length larger than the fixed-size DH-HMAC-CHAP response content. No successful authentication is required, so PR:N is appropriate for CVSS-style reasoning. This is network reachable when NVMe/TCP or another affected NVMe Fabrics transport is exposed, but real-world exposure is usually limited to storage or data-center networks rather than the public Internet. Namespaces do not materially reduce the remote pre-auth nature of the issue.

4. Severity interpretation
This behaves like an actionable Moderate issue rather than ordinary Moderate because it is a pre-authentication kernel memory disclosure in a storage target protocol. It is not an Important-class memory corruption bug by itself because there is no write primitive, UAF, refcount misuse, object confusion, or demonstrated LPE path. The paranoid score is raised for manual-review sensitivity because leaked slab memory may contain sensitive kernel or workload data, but the supported impact remains confidentiality-only.

5. One-sentence report phrase
An unauthenticated NVMe initiator can receive uninitialized kernel slab bytes from the AUTH_RECEIVE response buffer during the pre-authentication handshake, causing a network-reachable confidentiality leak in NVMe target authentication.

6. Manual review recommendation
MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK. This should not be auto-closed because it is a pre-authentication network-reachable kernel memory disclosure, even though no memory corruption or privilege escalation primitive is shown.

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

Patch: nvmet-auth: zero the AUTH_RECEIVE response buffer
Commit: 447b668faa14710f611e714031e3739ac3ec3a4f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=447b668faa14710f611e714031e3739ac3ec3a4f

Commit description:

nvmet_execute_auth_receive() allocates the response buffer with kmalloc()
sized by the host-supplied AUTH_RECEIVE allocation length, but the
DH-HMAC-CHAP builders write only a fixed-size message into it. The full
allocation length is then copied to the wire by nvmet_copy_to_sgl(), so a
remote initiator receives the bytes past the built message -- up to nearly
a page of uninitialized slab -- during the pre-authentication handshake.

Allocate the buffer with kzalloc() so the unwritten tail is zeroed before
it is sent; conforming responses are unaffected.

Fixes: db1312d ("nvmet: implement basic In-Band Authentication")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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=447b668faa14710f611e714031e3739ac3ec3a4f

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

The original Linux kernel CVE announcement for CVE-2026-80791 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80791

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: Not available
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS score: 6.5

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: 4
  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).