[CVE-2026-80789][MODERATE 7.0] nvmet-tcp: bound SGL data length before allocating command buffers [ Upstream

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

CVE: CVE-2026-80789
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: nvmet-tcp: bound SGL data length before allocating command buffers [ Upstream
Commit: f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80789
Analysis date: Fri, 04 Sep 2026 17:28:37 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80789 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80789

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.

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

CVE-2026-80789	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80789 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:N/I:N/A:H';CWE-770;CWE-789;**CWE-400;BEST CVSS score: '6.5';DESCR 'An unbounded allocation in the NVMe/TCP target path occurs because nvmet_tcp_map_data reads sgl length from a host supplied SGL descriptor and can pass that value to sgl_alloc before transfer length validation runs. A remote peer on the storage network can trigger this with a crafted non-inline transport SGL data-block descriptor for a write command, causing large kernel memory allocations that remain pinned while the command waits for H2C data. For the CVSS the PR:N is used because default NVMe/TCP target deployments do not require a local user account or kernel privileges once the peer can reach the target portal and complete Fabrics connect. The issue is network reachable within the NVMe/TCP storage network, but these targets are usually deployed on isolated data center or storage networks rather than the public Internet. Impact is denial of service through kernel memory exhaustion, with no evidence of information disclosure or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 7)	YES	REMOTE KASAN NVME NETWORK LINUS KPANIC  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=5

1. ActionableScore
* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Remote reachable / network-triggerable: +2. A peer that can reach the NVMe/TCP target portal can send a crafted command over TCP.
* Reliable kernel crash / strong DoS: +1. The host-controlled SGL length can reach `sgl_alloc()` before validation and drive very large kernel memory allocations.
* Availability impact realistic: +1. The allocation can remain pinned while the command waits for H2C data, and the pattern is repeatable across queues and connections.
* Important filesystem/storage path: +1. The affected code is in the NVMe/TCP target storage path.
* Practical exploit chain demonstrated or strongly implied: +1 for paranoid score only. The commit describes a concrete crafted non-inline SGL write request and runtime verification of large pinned allocations.
* No memory corruption signal. The patch supports resource exhaustion, not UAF, OOB write, type confusion, or arbitrary write.
* No confidentiality or integrity signal. The demonstrated impact is memory exhaustion DoS.

3. Reachability analysis
An unauthenticated or effectively unauthenticated remote peer can trigger the issue if it can reach the NVMe/TCP target portal and complete Fabrics connect. No local account on the victim is required. NVMe/TCP targets are usually deployed in isolated storage or data-center networks rather than exposed to the public Internet, so this is best treated as network-reachable within a storage network, not broad Internet exposure. Containers and namespaces are not the main privilege boundary here because the trigger is remote protocol input to the target service.

4. Severity interpretation
This is stronger than an ordinary Moderate resource leak because allocation size is host-controlled, can be very large, and can remain pinned pending unsatisfied data transfer. It does not look like Important-class memory corruption because the patch only bounds allocation length before `sgl_alloc()` and does not show overwrite, UAF, stale pointer reuse, or privilege escalation. The practical severity is Actionable Moderate, with manual review justified due to remote unauthenticated storage-network DoS.

5. One-sentence report phrase
A remote peer with access to an NVMe/TCP target can supply an oversized non-inline SGL length that reaches kernel buffer allocation before transfer validation, causing large pinned allocations and denial of service through memory exhaustion.

6. Manual review recommendation
MANUAL CHECK REQUIRED. The bug is network reachable in NVMe/TCP target deployments and has a concrete repeatable memory exhaustion path, even though it is not a demonstrated memory corruption or privilege escalation issue.

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

Patch: nvmet-tcp: bound SGL data length before allocating command buffers [ Upstream
Commit: f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5

Changed files:
  drivers/nvme/target/tcp.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=f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5

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

The original Linux kernel CVE announcement for CVE-2026-80789 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80789

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:N/I:N/A:H
  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: 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).