[CVE-2026-53148][IMPORTANT] thunderbolt: Clamp XDomain response data copy to allocation size

[CVE-2026-53148][IMPORTANT] thunderbolt: Clamp XDomain response data copy to allocation size

[AL-KERNEL]

CVE: CVE-2026-53148
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: thunderbolt: Clamp XDomain response data copy to allocation size
Commit: 0b334279a82d79fb4723bd4f614305de1ab69caa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0b334279a82d79fb4723bd4f614305de1ab69caa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53148
Analysis date: Thu, 25 Jun 2026 19:24:26 -0400
ActionableScore: 8
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A malicious Thunderbolt XDomain peer can provide an oversized response length that causes `tb_xdp_properties_request()` to copy past a `kcalloc` buffer, resulting in kernel heap corruption with realistic DoS and plausible privilege-escalation impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-53148 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53148

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: IMPORTANT
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-2026-53148	IMPORTANT	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-122;*CWE-20;CWE-120;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '8.8';DESCR 'A kernel heap out-of-bounds write exists in the Thunderbolt XDomain properties request path because tb_xdp_properties_request() copies response data using a length taken from the peer response header without ensuring that the cumulative offset stays within the allocated data buffer. A malicious XDomain peer can advertise a response length larger than the declared data_length and cause memcpy to write past the kcalloc allocation. For the CVSS the PR:N is used because the attacker does not need an account or privileges on the victim once a malicious peer can communicate on the local Thunderbolt/USB4 fabric. The issue is not Internet reachable and should be treated as adjacent local-bus exposure rather than AV:N. Impact is at least denial of service via kernel memory corruption and in the paranoid case may include confidentiality and integrity impact due to a kernel heap overwrite primitive. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-53148  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Adjacent local-bus / device peer influence: +1
  A malicious Thunderbolt / USB4 XDomain peer can influence the response header and data copied by the kernel.

* Memory corruption, strong corruption primitive: +2
  The bug is an out-of-bounds heap write past a `kcalloc` allocation via `memcpy`.

* Strong LPE plausibility: +2
  Kernel heap OOB writes with peer-controlled response data are plausible privilege-escalation candidates, even if no full exploit chain is shown.

* Reliable kernel crash / strong DoS: +1
  Writing beyond the allocated buffer can realistically crash the kernel.

* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs in the Thunderbolt XDomain device-management path, a highly trusted kernel subsystem.

* Confidentiality impact plausible: +1
  Heap corruption can plausibly affect kernel object integrity and potentially expose sensitive state in worst case.

* Integrity impact plausible: +1
  A heap overwrite can plausibly corrupt adjacent kernel objects.

* Physical-only or rare hardware-only condition: -2
  The issue is not Internet reachable. It requires access to a Thunderbolt / USB4 XDomain peer path.

Paranoid score adds stronger weight to the reliability and impact of a peer-controlled kernel heap overwrite, reaching 8.

## 3. Reachability analysis

The attacker does not need a local user account on the victim system, but must be able to act as a malicious Thunderbolt / USB4 XDomain peer. This is adjacent local-bus exposure, not normal network exposure. Namespaces and containers do not meaningfully affect reachability because the trigger is through device / fabric interaction rather than a local syscall interface. The path is configuration and hardware dependent, but Thunderbolt / USB4 systems are common enough that this should not be treated as a purely theoretical bug.

## 4. Severity interpretation

This behaves more like an Important-class kernel memory corruption issue than an ordinary Moderate DoS. The demonstrated primitive is a kernel heap out-of-bounds write, not only a warning, NULL dereference, or resource leak. Realistic exploitation may be constrained by Thunderbolt topology, IOMMU/security policy, heap layout, and XDomain availability. However, the corruption primitive is strong enough that auto-closing as low-risk DoS would be unsafe.

## 5. One-sentence report phrase

A malicious Thunderbolt XDomain peer can provide an oversized response length that causes `tb_xdp_properties_request()` to copy past a `kcalloc` buffer, resulting in kernel heap corruption with realistic DoS and plausible privilege-escalation impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a peer-influenced kernel heap OOB write in a privileged device-management subsystem. Even though exposure is adjacent / local-bus rather than Internet remote, the primitive is strong enough to require manual review.

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

Patch: thunderbolt: Clamp XDomain response data copy to allocation size
Commit: 0b334279a82d79fb4723bd4f614305de1ab69caa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0b334279a82d79fb4723bd4f614305de1ab69caa

Commit description:

tb_xdp_properties_request() derives the per-packet copy length from
the response header without checking that it fits in the previously
allocated data buffer.  A malicious peer can set its length field
larger than the declared data_length, causing memcpy to write past
the kcalloc allocation.

Clamp the per-packet copy length so that the cumulative offset
never exceeds data_len.

Fixes: cdae7c0 ("thunderbolt: Add support for XDomain properties")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/thunderbolt/xdomain.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=0b334279a82d79fb4723bd4f614305de1ab69caa

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

The original Linux kernel CVE announcement for CVE-2026-53148 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53148

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:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 8.8

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: 7
  Paranoid ActionableScore: 8

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).