[CVE-2026-99026][LOW] net: team: free skb when broadcast has no txable port

[CVE-2026-99026][LOW] net: team: free skb when broadcast has no txable port

[AL-KERNEL]

CVE: CVE-2026-99026
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: team: free skb when broadcast has no txable port
Commit: 961563117626f4681623077ec0cfd86f86da0d49
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=961563117626f4681623077ec0cfd86f86da0d49
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99026
Analysis date: Mon, 26 Oct 2026 22:47:57 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A local AF_PACKET sender can leak an skb and its socket write-memory charge when team broadcast transmission finds no usable port, potentially exhausting that socket’s send budget.

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

The original Linux kernel CVE announcement for CVE-2026-99026 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99026

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-2026-99026	LOW	https://www.kernelcve.org/list/?q=CVE-2026-99026 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: 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:L';*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: '3.3';DESCR 'The team broadcast transmit path can return NETDEV_TX_OK when no port is txable without consuming the original skb. AF_PACKET transmission then loses ownership while the skb and its socket write memory charge remain retained. The demonstrated primitive is a persistent resource leak that can exhaust the affected socket send budget and disrupt further transmission. Host wide memory exhaustion is not established because triggering requires a specific team port and carrier state and accumulation may be constrained by socket accounting. For the CVSS the PR:L value reflects that reliable triggering requires local packet transmission access and normally CAP_NET_RAW or equivalent delegated access. There is no evidence of UAF, OOB access, information disclosure, memory corruption, or privilege escalation. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 3.3 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 4.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	SIMPLEFIX NETWORK SKB LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; no technically supported additional impact.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 — Concrete persistent kernel resource leak: when no team port is transmit-capable, `bc_transmit()` returned without consuming the original skb, despite `team_xmit()` reporting `NETDEV_TX_OK`. The skb and AF_PACKET socket write-memory charge were consequently retained.
* +0 — The affected socket’s send budget can be exhausted, but host-wide memory exhaustion, kernel crash, or persistent system-wide denial of service is not established.
* No UAF, OOB access, shared-backing write, memory corruption, authorization bypass, confidentiality impact, or integrity impact is shown.
* NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of corrupted structured state.
* NEW53/B3-PENDING does not apply: no write to shared or file-backed storage is present.
* No reachability bonus: below-host-admin access to the complete topology configuration and trigger sequence is not established.

3. Reachability analysis

The leak is triggered through local AF_PACKET transmission while a team broadcast device has no transmit-capable port. Packet transmission normally requires `CAP_NET_RAW` or equivalent delegated access. Creating/configuring the team topology, controlling port states, or forcing carrier may additionally require `CAP_NET_ADMIN`, but the supplied evidence does not resolve whether the sender also performs those setup operations or merely uses an existing configuration. The governing capability namespaces and complete namespace-scoped trigger are therefore unknown. No special hardware or timing race is required.

4. Primitive and severity reading

The exact primitive is a missing skb consumption/free operation causing an skb and socket write-memory accounting leak. This is CLASS_C resource/availability behavior, not a lifetime violation involving stale use. The demonstrated effect is constrained disruption of subsequent sends on the affected socket. Broader memory exhaustion is speculative. There is no Important-class corrupt or trust-boundary primitive, so automatic Moderate handling remains appropriate.

5. One-sentence report phrase

A local AF_PACKET sender can leak an skb and its socket write-memory charge when team broadcast transmission finds no usable port, potentially exhausting that socket’s send budget.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch establishes a constrained resource leak without memory corruption, authorization bypass, or host-wide denial of service.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: team: free skb when broadcast has no txable port
Commit: 961563117626f4681623077ec0cfd86f86da0d49
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=961563117626f4681623077ec0cfd86f86da0d49

Commit description:

bc_transmit() sends the original skb through the last txable port.
When no port is txable, it returns false without consuming the skb, but
team_xmit() still returns NETDEV_TX_OK. AF_PACKET sends then retain the
skb and its socket write-memory charge.

A TX-enabled, link-down port keeps the broadcast transmit op installed.
Carrier can stay up through a second link-up, TX-disabled port or be
forced on by userspace. Free the original skb on the no-port path while
leaving the existing drop accounting intact.

Discovered by Sashiko during review of previous commit.

Cc: stable@vger.kernel.org
Fixes: 5fc8899 ("team: add broadcast mode")
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Link: https://patch.msgid.link/20261001182326.572045-3-bestswngs@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/team/team_mode_broadcast.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=961563117626f4681623077ec0cfd86f86da0d49

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

The original Linux kernel CVE announcement for CVE-2026-99026 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99026

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:L
  The Best / paranoid CVSS score: 3.3

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: unknown
  Paranoid ActionableScore: 1

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).