[CVE-2026-98375][MODERATE REGULAR] xen/netfront: drop RX packets with a short Ethernet header handle_incoming_queue() pulls pull_to bytes into the head before calling eth_type_trans(). pull_to is the length of the first RX slot, capped at RX_COPY_THRESHOLD, and that length comes from the backend. Nothing checks it against ETH_HLEN. If the first slot is shorter than ETH_HLEN and more slots follow, the head ends up shorter than an Ethernet header while skb->len is longer, and eth_type_trans() BUG()s in __skb_pull(). If the whole packet is shorter than ETH_HLEN, eth_type_trans() reads the header past the end of the data instead. Pull at least ETH_HLEN, and drop the packet if that fails, which also drops packets too short to hold an Ethernet header. This also checks the return value of the pull, which was ignored. Fixes: 0d16021 ("xen: add virtual network device driver") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik <josef@toxicpanda.com> Link: https://patch.msgid.link/20261007-b4-xen-netfront-short-head-v1-1-12d7113a7e4e@toxicpanda.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>

[CVE-2026-98375][MODERATE REGULAR] xen/netfront: drop RX packets with a short Ethernet header handle_incoming_queue() pulls pull_to bytes into the head before calling eth_type_trans(). pull_to is the length of the first RX slot, capped at RX_COPY_THRESHOLD, and that length comes from the backend. Nothing checks it against ETH_HLEN. If the first slot is shorter than ETH_HLEN and more slots follow, the head ends up shorter than an Ethernet header while skb->len is longer, and eth_type_trans() BUG()s in __skb_pull(). If the whole packet is shorter than ETH_HLEN, eth_type_trans() reads the header past the end of the data instead. Pull at least ETH_HLEN, and drop the packet if that fails, which also drops packets too short to hold an Ethernet header. This also checks the return value of the pull, which was ignored. Fixes: 0d16021 ("xen: add virtual network device driver") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik <josef@toxicpanda.com> Link: https://patch.msgid.link/20261007-b4-xen-netfront-short-head-v1-1-12d7113a7e4e@toxicpanda.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>

[AL-KERNEL]

CVE: CVE-2026-98375
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: xen/netfront: drop RX packets with a short Ethernet header handle_incoming_queue() pulls pull_to bytes into the head before calling eth_type_trans(). pull_to is the length of the first RX slot, capped at RX_COPY_THRESHOLD, and that length comes from the backend. Nothing checks it against ETH_HLEN. If the first slot is shorter than ETH_HLEN and more slots follow, the head ends up shorter than an Ethernet header while skb->len is longer, and eth_type_trans() BUG()s in __skb_pull(). If the whole packet is shorter than ETH_HLEN, eth_type_trans() reads the header past the end of the data instead. Pull at least ETH_HLEN, and drop the packet if that fails, which also drops packets too short to hold an Ethernet header. This also checks the return value of the pull, which was ignored. Fixes: 0d16021 ("xen: add virtual network device driver") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik <josef@toxicpanda.com> Link: https://patch.msgid.link/20261007-b4-xen-netfront-short-head-v1-1-12d7113a7e4e@toxicpanda.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Commit: 089e58805c452e52179482b1025a8e309a57f801
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=089e58805c452e52179482b1025a8e309a57f801
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98375
Analysis date: Fri, 09 Oct 2026 22:05:22 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
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-2026-98375 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98375

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 REGULAR
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-2026-98375	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98375 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (independent Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-125;*CWE-20;CWE-252;Other CVSS 'AV:A/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.8';DESCR 'A Xen network backend can provide an RX packet whose first slot is shorter than ETH_HLEN while additional slots make the total skb length appear valid. The netfront receive path can then call eth_type_trans with an insufficient linear Ethernet header which can trigger a BUG in __skb_pull and crash the guest kernel. A packet whose total length is shorter than ETH_HLEN can instead cause an out of bounds read past the valid skb data. For the CVSS the PR:L value is used for the paranoid score because a reduced privilege driver domain or backend service may control the shared RX ring without having unrestricted host root privileges. The base assessment uses PR:H for conventional Xen deployments where backend control normally requires dom0 level access. This issue is adjacent rather than ordinarily Internet reachable because the attacker must control or compromise the Xen network backend. Impact is at least denial of service against the guest and the out of bounds read justifies limited confidentiality and integrity impact for manual review in the paranoid assessment.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	SIMPLEFIX NETWORK SKB HARDWARE PACKET  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

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

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Reliable kernel crash / strong DoS. A backend-controlled short first RX slot followed by additional fragments can leave the linear head shorter than ETH_HLEN. The subsequent `eth_type_trans()` call can trigger `BUG()` through `__skb_pull()`.
* +0 Limited OOB read. If the entire packet is shorter than ETH_HLEN, `eth_type_trans()` reads beyond valid skb data. No disclosure path, subsequent write, or security-sensitive value influence is established.

Negative signals:

* No negative points. Backend privilege is unresolved, so no host-admin penalty is applied.
* No race penalty. The malformed slot layout provides a deterministic trigger after backend control is obtained.
* No niche-subsystem or hardware penalty. Xen deployment is a prerequisite, but no unusual physical hardware is required.

Important non-awarded signals:

* Direct remote reachability is not established. Ordinary network traffic is not shown to control Xen RX slot boundaries without backend cooperation.
* Local unprivileged reachability is not established.
* No UAF, stale lifetime operation, controlled reclaim, OOB write, arbitrary write, or callback influence exists.
* Confidentiality is not awarded because the internal OOB read is not shown to reach userspace, the backend, or another observable output.
* Integrity is not awarded because no write or persistent state modification is demonstrated.
* No extra Availability point is awarded because it would double-count the same kernel crash.
* B5-R is not established because there is no heap OOB write, retry-accumulated index, or later consumption of corrupted written state.
* B3-PENDING is not established because there is no write to shared or file-backed storage.
* B4-PENDING is not established because no authorization decision or mandatory security guard is bypassed.

3. Reachability analysis

The immediate input is controlled by a Xen network backend through the length and arrangement of RX slots. A malicious or compromised backend can construct the short first slot required for the crash or OOB-read paths.

The supplied evidence does not establish whether the complete attacker is conventional dom0 with host-administrator powers or a reduced-privilege driver domain or backend service. Therefore `HostAdminRequired=UNKNOWN`. Numeric host UID 0 is likewise unresolved.

The operation is not namespace-capability based, and an attacker-created user or network namespace does not provide control over the Xen backend ring. No prior sysctl, boot option, or special physical hardware is identified beyond running the guest with Xen netfront and an associated backend.

External Ethernet traffic alone is not shown to preserve attacker-selected malformed RX slot geometry through the backend. The trigger is deterministic rather than a race once backend control is available.

4. Primitive and severity interpretation

The first demonstrated behavior is an invalid skb layout followed by a `BUG()` when `eth_type_trans()` attempts to consume an Ethernet header from an insufficient linear head. This is a strong guest availability failure.

The second behavior is a read beyond the valid skb packet data when the complete packet is shorter than ETH_HLEN. It is a limited read-only OOB primitive with no established disclosure or subsequent corruption sink.

There is no stale storage, active structured-object UAF, repeated release, refcount mutation, or lifetime violation. There is also no authorization bypass or shared-backing ownership violation.

The issue is therefore `CLASS_C`. The demonstrated consequence is guest kernel crash or invalid internal read. Stronger confidentiality, integrity, privilege-escalation, or cross-domain corruption consequences remain unsupported.

`ImportantCandidate=NO` because no independently useful corruption or boundary-bypass primitive remains after excluding the crash. `AutoDowngradeAllowed=YES` because this is a constrained crash/OOB-read case without unresolved write or lifetime leverage. Operational severity is ordinary Moderate and depends on control or compromise of the Xen backend.

5. One-sentence report phrase

A malicious or compromised Xen network backend can provide an RX packet with an undersized Ethernet header and trigger a guest kernel BUG or a limited out-of-bounds read, but no disclosure, write primitive, or privilege escalation is established.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm the product-specific Xen backend privilege boundary and whether any deployed backend can be controlled below host-administrator privilege, but the supplied patch does not preserve an Important-grade primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: xen/netfront: drop RX packets with a short Ethernet header handle_incoming_queue() pulls pull_to bytes into the head before calling eth_type_trans(). pull_to is the length of the first RX slot, capped at RX_COPY_THRESHOLD, and that length comes from the backend. Nothing checks it against ETH_HLEN. If the first slot is shorter than ETH_HLEN and more slots follow, the head ends up shorter than an Ethernet header while skb->len is longer, and eth_type_trans() BUG()s in __skb_pull(). If the whole packet is shorter than ETH_HLEN, eth_type_trans() reads the header past the end of the data instead. Pull at least ETH_HLEN, and drop the packet if that fails, which also drops packets too short to hold an Ethernet header. This also checks the return value of the pull, which was ignored. Fixes: 0d16021 ("xen: add virtual network device driver") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik <josef@toxicpanda.com> Link: https://patch.msgid.link/20261007-b4-xen-netfront-short-head-v1-1-12d7113a7e4e@toxicpanda.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Commit: 089e58805c452e52179482b1025a8e309a57f801
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=089e58805c452e52179482b1025a8e309a57f801

Changed files:
  drivers/net/xen-netfront.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=089e58805c452e52179482b1025a8e309a57f801

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

The original Linux kernel CVE announcement for CVE-2026-98375 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98375

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.8

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

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).