[CVE-2026-53223][MODERATE 7.0] net: guard timestamp cmsgs to real error queue skbs [ Upstream

[CVE-2026-53223][MODERATE 7.0] net: guard timestamp cmsgs to real error queue skbs [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53223
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: guard timestamp cmsgs to real error queue skbs [ Upstream
Commit: 24a0d548d3a765cd4558224e4f8e06e14cba26e3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24a0d548d3a765cd4558224e4f8e06e14cba26e3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53223
Analysis date: Thu, 25 Jun 2026 07:13:11 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum**:: Actionable Moderate at minimum. Manual review is justified because the patch supports kernel heap disclosure and hardened usercopy crash, but not a clear write primitive or LPE path
Manual review required: YES

Summary:
AF_PACKET outgoing skbs can be mistaken for socket error queue skbs in timestamp cmsg handling, allowing a local CAP_NET_RAW capable process to trigger hardened usercopy DoS or potentially disclose adjacent kernel heap contents.

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

The original Linux kernel CVE announcement for CVE-2026-53223 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53223

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-53223	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H';CWE-843;CWE-125;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H';BEST CVSS score: '7.1';DESCR 'skb_is_err_queue used PACKET_OUTGOING as the only marker for skbs from the socket error queue, but AF_PACKET outgoing taps can also carry PACKET_OUTGOING while their control buffer belongs to AF_PACKET. With timestamping and SO_RXQ_OVFL enabled, generic timestamp cmsg handling can interpret AF_PACKET control buffer data as sock_exterr_skb opt_stats and may emit SCM_TIMESTAMPING_OPT_STATS using skb len and skb data. For non linear skbs this can copy past the linear skb head, which can trigger hardened usercopy or disclose adjacent kernel heap contents. For the CVSS the PR:L is used because triggering requires a local process able to use AF_PACKET and socket options, commonly via CAP_NET_RAW or a delegated network capability rather than full host root. The issue is not directly network reachable, although local traffic generation and outgoing packet taps are part of the trigger. Impact is denial of service and kernel memory disclosure. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	REMOTE INIT SKB HARDWARE TEST PACKET  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: Actionable Moderate at minimum. Manual review is justified because the patch supports kernel heap disclosure and hardened usercopy crash, but not a clear write primitive or LPE path**

## 2. Signal breakdown

Conservative signals:

* Local reduced privilege trigger: +1
  Triggering requires a local process able to use AF_PACKET and timestamping options, commonly requiring CAP_NET_RAW or delegated network capability, not full host root.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly says non linear skbs can trigger hardened usercopy.

* Confidentiality impact plausible: +1
  The path can copy past the skb linear head and disclose adjacent heap contents.

* Broad networking/socket exposure: +1
  The bug is in generic socket timestamp cmsg handling and AF_PACKET interaction, not a rare driver-only path.

Paranoid additional signal:

* Local high-control packet socket data path: +1
  AF_PACKET plus socket options and outgoing packet taps give meaningful local control over packet delivery context, though this is weaker than io_uring or BPF.

Not counted:

* Remote reachable: +0
  No direct network-only trigger is shown.

* Privilege escalation plausible: +0
  The patch supports OOB read and DoS, but no write primitive, UAF reclaim, callback control, or refcount takeover.

* Generic strong memory corruption: +0
  This is primarily invalid struct interpretation leading to OOB read, not an OOB write or UAF.

## 3. Reachability analysis

A local process can trigger the affected path by using AF_PACKET outgoing taps together with timestamping and SO_RXQ_OVFL conditions. In typical deployments AF_PACKET requires CAP_NET_RAW, but this may be available to container root, sandboxed services, or processes with delegated network capability. User namespaces may lower practical reachability depending on distro configuration. The issue is not directly network reachable because packet traffic alone does not invoke the vulnerable userspace receive path without a local AF_PACKET socket and options.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because the described failure mode includes kernel heap disclosure, not only a warning or crash. It is best treated as Actionable Moderate and manually reviewed. It does not reach a strong Important conclusion on the conservative evidence because there is no demonstrated write primitive, UAF reuse, type confusion with object replacement, or practical LPE chain.

## 5. One-sentence report phrase

AF_PACKET outgoing skbs can be mistaken for socket error queue skbs in timestamp cmsg handling, allowing a local CAP_NET_RAW capable process to trigger hardened usercopy DoS or potentially disclose adjacent kernel heap contents.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch context explicitly supports an OOB read and possible kernel heap disclosure in a networking socket path, which should not be auto-closed even without a demonstrated privilege escalation primitive.

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

Patch: net: guard timestamp cmsgs to real error queue skbs [ Upstream
Commit: 24a0d548d3a765cd4558224e4f8e06e14cba26e3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24a0d548d3a765cd4558224e4f8e06e14cba26e3

Changed files:
  net/socket.c
  include/net/sock.h
  net/core/skbuff.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=24a0d548d3a765cd4558224e4f8e06e14cba26e3

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

The original Linux kernel CVE announcement for CVE-2026-53223 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53223

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:H/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
  The Best / paranoid CVSS score: 7.1

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: 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: 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).