[CVE-2026-53235][MODERATE 7.0] net: add pskb_may_pull() to skb_gro_receive_list() [ Upstream

[CVE-2026-53235][MODERATE 7.0] net: add pskb_may_pull() to skb_gro_receive_list() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53235
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: add pskb_may_pull() to skb_gro_receive_list() [ Upstream
Commit: 9e636c995b7beeb74ea882968248752821c244c4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e636c995b7beeb74ea882968248752821c244c4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53235
Analysis date: Fri, 26 Jun 2026 04:37:22 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A missing pskb_may_pull() check in skb_gro_receive_list() can allow crafted network traffic reaching the GRO fraglist path to trigger a BUG_ON in __skb_pull(), causing a remote kernel crash DoS without evidence of privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-53235 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53235

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-2026-53235	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-617;*CWE-20;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'skb_gro_receive_list() can call skb_pull() with a non zero GRO offset before ensuring that the referenced bytes are present in the linear skb area. When packets arrive through napi_gro_frags(), skb_headlen can be 0 while the parsed GRO offset is non zero, causing an internal skb length invariant failure and a BUG_ON in __skb_pull(). This can crash the kernel and cause denial of service when the affected GRO fraglist receive path is reachable by network traffic. For the CVSS the PR:N because the attacker does not need local access or privileges on the target, only network reachability to a path that exercises the affected GRO processing. The base score uses AC:H because reliable triggering depends on GRO fraglist conditions, driver behavior, and packet layout. The paranoid score uses AC:L as the highest still defensible interpretation if the deployment exposes the vulnerable GRO path to attacker controlled traffic. Impact is denial of service only based on the visible primitive, with no concrete evidence of information disclosure or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-53235  SKIP The Fixes patch not applied yet, so unlikely that actual: 8d95dc474f85481652a0e422d2f1f079de81f63c YES  NO NO unknown 	MAYBE	REMOTE INIT NOMEMCHK SIMPLEFIX SKB LINUS KPANIC  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. The affected path is GRO receive processing and can be reached by crafted network traffic when the relevant GRO fraglist path is active.
* Reliable kernel crash / strong DoS: +1. The described failure reaches BUG_ON(skb->len < skb->data_len) in __skb_pull(), causing a kernel crash.
* Common networking core path or packet-processing path: +1. The bug is in net/core/gro.c and affects centralized GRO handling for TCP, UDP, and future callers.
* Hard or configuration-dependent trigger: -1. Reliable triggering depends on napi_gro_frags(), GRO fraglist behavior, driver/NIC behavior, and packet layout.

Paranoid delta:

* Broad/default/common subsystem exposure: +1. GRO is a common networking optimization in production kernels, even if the exact fraglist condition is not universal.
* Availability impact realistic: +1. If the affected GRO path is exposed, the result is a host-wide kernel BUG and repeatable remote DoS.
* No timing penalty in paranoid case. The condition is packet-shape and receive-path dependent rather than a narrow race.

Not counted:

* No generic memory corruption. The visible primitive is invariant violation leading to BUG_ON, not UAF, OOB write, double free, or controlled overwrite.
* No privilege escalation plausible signal. The patch does not show a realistic corruption primitive beyond crash.
* No confidentiality or integrity impact. There is no read-back, information leak, write primitive, or ownership bypass.

## 3. Reachability analysis

An attacker with network reachability to an interface using the affected GRO fraglist receive path may trigger the bug with crafted traffic that results in non-linear skb data and a non-zero GRO offset. No local account or target-side privileges are required, so PR is effectively none for the network-triggered scenario. The path is not a rare admin-only ioctl or debug interface, but practical reachability depends on NIC driver behavior, GRO configuration, and whether packets arrive through napi_gro_frags(). Containers and namespaces are not central to triggering because this is a packet receive path rather than a local control-plane API.

## 4. Severity interpretation

This behaves as an actionable network DoS, not as a proven Important-class memory corruption issue. The conservative score is borderline because the trigger depends on specific GRO fraglist conditions. The paranoid score reaches Actionable Moderate because the bug is network reachable, in core packet processing, and can crash the kernel. It should not be auto-closed as an ordinary Moderate without confirming exposure of the affected GRO path.

## 5. One-sentence report phrase

A missing pskb_may_pull() check in skb_gro_receive_list() can allow crafted network traffic reaching the GRO fraglist path to trigger a BUG_ON in __skb_pull(), causing a remote kernel crash DoS without evidence of privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: network-reachable kernel crash in core networking/GRO code. The impact appears limited to DoS, but exposure depends on realistic driver and GRO receive-path conditions and should be validated manually.

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

Patch: net: add pskb_may_pull() to skb_gro_receive_list() [ Upstream
Commit: 9e636c995b7beeb74ea882968248752821c244c4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9e636c995b7beeb74ea882968248752821c244c4

Changed files:
  net/core/gro.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=9e636c995b7beeb74ea882968248752821c244c4

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

The original Linux kernel CVE announcement for CVE-2026-53235 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53235

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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 7.5

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: 4
  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).