[CVE-2026-68287][MODERATE 7.0] drop_monitor: fix size calculations for 64-bit attributes [ Upstream

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

CVE: CVE-2026-68287
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drop_monitor: fix size calculations for 64-bit attributes [ Upstream
Commit: 4a9e30764e80693bcf875c776170edce20f94fe0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a9e30764e80693bcf875c776170edce20f94fe0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68287
Analysis date: Mon, 10 Aug 2026 19:04:16 -0400
ActionableScore: 5
ActionableScore lower bound: 2
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
drop_monitor underestimates skb size for 64 bit netlink attributes on affected 32 bit systems, allowing packet alert report construction to hit skb_over_panic and crash the kernel when the feature is enabled.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68287 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68287

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: NO

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-2026-68287	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-131;**CWE-400;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'drop_monitor can underestimate the skb size needed for 64 bit netlink attributes because nla_put_u64_64bit may add an alignment padding attribute on affected 32 bit systems. When packet alert reporting builds the message, the skb can be too small and __nla_reserve or skb_put can hit skb_over_panic, causing a kernel crash. For the CVSS the PR:N is used in the paranoid case because an attacker may not need local privileges if packet alert mode is already enabled and the target can be reached with traffic that causes packet drops. The issue is not a proven memory corruption primitive and the expected impact is denial of service only. Practical exposure is limited to systems using drop_monitor packet alert mode on affected 32 bit architectures without efficient unaligned access.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE DANGER SIMPLEFIX SKB HARDWARE LINUS PACKET  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Paranoid score signals:

* Remote reachable / network-triggerable: +2. If drop_monitor packet alert mode is already enabled, an external or adjacent host may be able to generate packet drops that cause report construction.
* Memory layout invariant restoration: +1. The patch fixes inconsistent skb size budgeting for 64 bit netlink attributes that may require extra alignment padding.
* Reliable kernel crash / strong DoS: +1. The commit explicitly states that the underestimation can lead to skb_over_panic in __nla_reserve or skb_put.
* Availability impact realistic: +1. The failure mode is a kernel panic, so the impact is system-wide availability loss once the vulnerable reporting path is reached.
* Rare and configuration-dependent exposure: -1. The issue requires 32 bit architectures without CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS and drop_monitor packet alert reporting.

Conservative score signals:

* Memory layout invariant restoration: +1.
* Reliable kernel crash / strong DoS: +1.
* Requires admin or CAP_NET_ADMIN in typical deployments: -2. Enabling and configuring drop_monitor packet alert mode normally requires privileged control.
* Rare and configuration-dependent exposure: -1.
* Availability impact realistic: +1.

No C or I impact is counted because the described failure is skb_over_panic, not a demonstrated overwrite primitive, UAF, info leak, or privilege escalation path.

## 3. Reachability analysis

Typical triggering requires privileged configuration of drop_monitor packet alert mode, so the conservative interpretation is local privileged or admin-assisted DoS. In the paranoid interpretation, if the feature is already enabled by an administrator or monitoring service, an attacker with network adjacency may be able to cause packet drops and indirectly trigger vulnerable report generation without local privileges. Namespace delegation could matter only if an untrusted container or service has enough netlink or CAP_NET_ADMIN-like control to configure drop_monitor. The exposure is limited by architecture and configuration requirements.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an Important vulnerability. The practical impact is kernel panic / DoS, and the patch does not show attacker-controlled memory corruption beyond a checked skb_over_panic condition. It should not be auto-closed blindly because the failure may be network-adjacent when packet alert mode is already enabled, but it lacks evidence for LPE, data corruption, or confidentiality impact.

## 5. One-sentence report phrase

drop_monitor underestimates skb size for 64 bit netlink attributes on affected 32 bit systems, allowing packet alert report construction to hit skb_over_panic and crash the kernel when the feature is enabled.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the realistic score depends heavily on deployment state: whether drop_monitor packet alert mode is enabled, whether affected 32 bit systems are in scope, and whether packet drops can be induced by untrusted network traffic.

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

Patch: drop_monitor: fix size calculations for 64-bit attributes [ Upstream
Commit: 4a9e30764e80693bcf875c776170edce20f94fe0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a9e30764e80693bcf875c776170edce20f94fe0

Changed files:
  net/core/drop_monitor.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=4a9e30764e80693bcf875c776170edce20f94fe0

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

The original Linux kernel CVE announcement for CVE-2026-68287 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68287

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 2
  Paranoid ActionableScore: 5

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 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).