[CVE-2026-80988][LOW] NTB: ntb_transport: Fail TX enqueue when the QP link is down

[CVE-2026-80988][LOW] NTB: ntb_transport: Fail TX enqueue when the QP link is down

[AL-KERNEL]

CVE: CVE-2026-80988
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: NTB: ntb_transport: Fail TX enqueue when the QP link is down
Commit: 5eca0d899a3be661a7e2caaaa7467a6fa15d756c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5eca0d899a3be661a7e2caaaa7467a6fa15d756c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80988
Analysis date: Fri, 11 Sep 2026 22:35:02 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80988 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80988

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: LOW
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-2026-80988	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80988 CHECK WITH IMPACT FROM ORIG NN LOW	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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'NTB transport returned success from ntb_transport_tx_enqueue when the QP link was down even though the skb was not queued and not consumed. The caller could then report NETDEV_TX_OK and forget the skb, causing one leaked skb for each transmit attempt that hits the link-down state. For the CVSS the PR:L is used because a local user or local process that can generate traffic through the configured NTB network device may be enough in some deployments, while reliable triggering still depends on the NTB link state. The issue is not directly Internet reachable and normally applies to systems using NTB between adjacent hosts or specialized local interconnects. Impact is denial of service through gradual memory exhaustion, with no supported confidentiality or integrity impact because the primitive is a resource leak rather than memory corruption.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)  SKIP CVE-2026-80988 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	SIMPLEFIX LEAK SKB PACKET  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap changed the score.

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. `ntb_transport_tx_enqueue()` returned success while not consuming or freeing the skb, so the caller could forget the skb and leak it.
* +0 Reliable kernel crash / strong DoS not awarded. The patch establishes gradual skb leakage, not an immediate kernel crash or panic.
* +0 Confidentiality and integrity not awarded. There is no UAF, OOB access, arbitrary write, disclosure path, authorization bypass, or ownership violation.
* +0 Local unprivileged trigger not awarded. A local process may generate traffic through an already configured NTB netdev, but the complete ability to reliably force the QP link-down condition is not established.
* +0 Remote reachability not awarded. NTB is a local or adjacent-host interconnect path, not an Internet-reachable packet-processing path.
* +0 Race/timing penalty not applied. The wording mentions racing link-down, but no materially hard or one-shot timing requirement is established for the resource leak condition.
* +0 Rare hardware penalty not applied. NTB is specialized hardware, but the prompt requires concrete evidence before subtracting based only on niche subsystem status.

Paranoid additional signal:

* +1 Sustained availability impact. If an attacker or faulty environment can repeatedly transmit while the QP link is down, the one-skb-per-attempt leak can accumulate toward memory exhaustion.

Non-awarded material signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Real UAF not demonstrated.
* Concrete repeated release/refcount mutation not demonstrated.
* Structured stale-object leverage not applicable.
* Weak LPE not awarded because the primitive is a resource leak, not memory corruption.
* Extra availability beyond sustained memory exhaustion not awarded.

3. Reachability analysis

The vulnerable path is reached through NTB transport TX enqueue, likely via `ntb_netdev` when packets are submitted while the QP link is down. A local process may be able to generate traffic through a configured NTB-backed network interface, but the supplied evidence does not prove that an ordinary user can create the NTB setup or control the link-down state. Therefore `HostAdminRequired=UNKNOWN`, not YES, because host-admin privilege is not positively established for the complete trigger. It is also not NO, because below-host-admin complete reachability is not positively established.

No namespace-scoped capability path is shown. `NamespaceScopedPrivilege=NO` for the supplied evidence. Prior setup of NTB hardware and an NTB network device is likely required, but the analysis does not subtract a penalty solely from that deployment fact. The issue is not directly network-reachable from ordinary remote traffic. It applies to systems using NTB between adjacent hosts or specialized interconnects.

4. Primitive and severity interpretation

The exact primitive is a kernel skb resource leak caused by a violated ownership/return-value contract. Returning 0 told the caller that the skb was accepted or consumed, but the transport did neither when the QP link was down. This is not an active structured UAF, not fixed stale storage, and not a double-release/refcount mutation. The demonstrated consequence is gradual memory leakage and possible DoS through resource exhaustion if repeated.

`PrimitiveClass=NONE` because no meaningful corruption, stale post-lifetime use, authorization bypass, or semantic ownership/COW violation is established. `ImportantCandidate=NO` because the issue is resource exhaustion only and lacks memory corruption or security-boundary leverage. `AutoDowngradeAllowed=YES` because the unresolved risk does not include UAF, repeated lifetime mutation, controlled corruption, or LPE evidence.

Likely operational severity is Low to ordinary Moderate. It may be worth fixing in normal maintenance, but it does not require Important-class manual escalation based on the supplied evidence.

5. One-sentence report phrase

NTB transport could leak one skb for each transmit attempt that hits a QP link-down state because TX enqueue returned success without consuming the packet, leading to possible local resource-exhaustion DoS but no demonstrated memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a concrete skb memory/resource leak with possible DoS only, and no UAF, repeated refcount mutation, arbitrary write, authorization bypass, or confidentiality/integrity primitive is established.

7. Call-site confidence

Call-site confidence: medium

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

Patch: NTB: ntb_transport: Fail TX enqueue when the QP link is down
Commit: 5eca0d899a3be661a7e2caaaa7467a6fa15d756c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5eca0d899a3be661a7e2caaaa7467a6fa15d756c

Commit description:

Commit f195a1a ("ntb: Drop packets when qp link is down") meant to
make ntb_transport_tx_enqueue() drop packets submitted while the QP link
is down, but it only returns 0 without consuming the packet. Zero means
success by this function's contract, so ntb_netdev reports NETDEV_TX_OK
and forgets the skb: nothing queued it, nothing frees it, and it leaks,
one skb for every transmit racing a link-down.

Return -ENOLINK instead, restoring the contract that a non-zero return
leaves the buffer owned by the caller. With the preceding patch,
ntb_netdev frees the skb on non-retryable enqueue failures and returns
NETDEV_TX_OK, so a packet racing with link-down is dropped without leaking
or entering a busy retry loop.

Fixes: f195a1a ("ntb: Drop packets when qp link is down")
Cc: stable@vger.kernel.org
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260817053519.4135287-4-den@valinux.co.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/ntb/ntb_transport.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=5eca0d899a3be661a7e2caaaa7467a6fa15d756c

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

The original Linux kernel CVE announcement for CVE-2026-80988 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80988

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:H/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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).