[CVE-2026-72296][MODERATE REGULAR] net: ife: require ETH_HLEN to be pullable in ife_decode()

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

CVE: CVE-2026-72296
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: ife: require ETH_HLEN to be pullable in ife_decode()
Commit: 70013f9163bef7fbd9fa62f81cf91b2a7ba66163
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=70013f9163bef7fbd9fa62f81cf91b2a7ba66163
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72296
Analysis date: Sat, 15 Aug 2026 23:25:14 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A malformed IFE frame can leave the inner Ethernet header non-pullable before eth_type_trans(), allowing an adjacent network attacker to crash the kernel when IFE decoding is configured.

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

The original Linux kernel CVE announcement for CVE-2026-72296 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72296

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: 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
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CVE-2026-72296	MODERATE	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:L/I:L/A:H';*CWE-20;CWE-125;CWE-754;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.6';DESCR 'A malformed IFE frame can reach ife_decode with only the outer IFE header and metadata made pullable while the inner Ethernet header is still shorter than ETH_HLEN in the skb linear data area. The decapsulated packet is then passed to eth_type_trans which expects the inner Ethernet header to be directly accessible and can crash the kernel when that assumption is false. For the CVSS the PR:N is used in the paranoid score because a sender of malformed IFE traffic does not need local privileges on the victim once an IFE decode action is configured. The issue is adjacent network reachable rather than Internet routable because IFE is an Ethernet level encapsulation and practical exploitation normally requires access to the same L2 or trusted switching domain where this tc action is deployed. Impact is at least denial of service via kernel crash. In the paranoid interpretation, limited confidentiality or integrity impact is kept for manual review sensitivity due to an invalid read around the inner Ethernet header, but there is no clear write primitive or UAF in this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)  SKIP CVE-2026-72296 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	DANGER SIMPLEFIX SKB IMPROVEONLY LINUS PACKET  INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  A malformed IFE Ethernet frame can trigger the path once an IFE decode action is configured. This is adjacent or L2 network reachable, not generally Internet routable.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly says the malformed frame can lead to a crash when the decapsulated packet reaches eth_type_trans() without a pullable inner Ethernet header.

* Rare AND difficult-to-reach subsystem/configuration: -1
  IFE is not a default common receive path. Practical exposure requires tc IFE action configuration.

Paranoid additional signal:

* Memory layout invariant restoration: +1
  The fix restores an skb pullability invariant by changing the required linear length from total_pull to total_pull + ETH_HLEN before a later Ethernet header access.

Not awarded:

* Generic memory corruption: +0
  The patch shows insufficient linear data validation and an invalid read/crash class issue, but no UAF, double free, OOB write, overwrite primitive, type confusion, or attacker-controlled reclaim.

* Privilege escalation plausible: +0
  No LPE primitive is supported by the patch.

* Confidentiality / Integrity impact: +0 conservative
  No disclosure path or write primitive is shown. A paranoid CVSS may keep C:L/I:L for manual-review sensitivity, but the actionable formula should not count it without a concrete primitive.

## 3. Reachability analysis

An attacker who can send malformed IFE traffic to an interface where IFE decoding is configured may trigger the bug without local privileges on the victim. The realistic attack surface is an adjacent Ethernet or trusted switching domain, because IFE is an Ethernet-level encapsulation and normally depends on local traffic-control setup. Namespaces do not materially reduce the sender-side privilege requirement, but configuring the vulnerable IFE action itself is administrative. This is not default-enabled on ordinary systems.

Call-site confidence: medium. The commit states that the caller passes the decapsulated skb to eth_type_trans(), and the one-line fix directly matches the missing ETH_HLEN pullability requirement.

## 4. Severity interpretation

This behaves more like a network-adjacent actionable Moderate or borderline manual-review issue than an Important-class kernel vulnerability. The practical impact is kernel crash / DoS from malformed packet input under a specific runtime configuration. The theoretical concern is an invalid read around skb linear data, but the patch does not support memory corruption beyond read-side invalid access, nor does it show a privilege escalation or data corruption primitive.

## 5. One-sentence report phrase

A malformed IFE frame can leave the inner Ethernet header non-pullable before eth_type_trans(), allowing an adjacent network attacker to crash the kernel when IFE decoding is configured.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue is packet-triggerable in a kernel networking path and can crash the kernel, even though it requires non-default IFE configuration and does not show a strong memory-corruption or privilege-escalation primitive.

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

Patch: net: ife: require ETH_HLEN to be pullable in ife_decode()
Commit: 70013f9163bef7fbd9fa62f81cf91b2a7ba66163
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=70013f9163bef7fbd9fa62f81cf91b2a7ba66163

Commit description:

ife decode may return after making only the outer IFE header and
metadata pullable. The caller then passes the decapsulated packet to
eth_type_trans(), which expects the inner Ethernet header to be
accessible from the linear data area.

With a malformed IFE frame, the inner Ethernet header may still be
shorter than ETH_HLEN in the linear area, which can lead to a crash in
the original code.

Fix this by extending the pull check in ife_decode() so that the inner
Ethernet header is also guaranteed to be pullable before returning.

Fixes: ef6980b ("introduce IFE action")
Cc: stable@vger.kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Yong Wang <edragain@163.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Link: https://patch.msgid.link/20260610183814.1648888-2-n05ec@lzu.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/ife/ife.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=70013f9163bef7fbd9fa62f81cf91b2a7ba66163

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

The original Linux kernel CVE announcement for CVE-2026-72296 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72296

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:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 7.6

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: 3
  Paranoid ActionableScore: 4

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).