[CVE-2026-45871][LOW] tpm: st33zp24: Fix missing cleanup on get_burstcount() error [ Upstream

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

CVE: CVE-2026-45871
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: tpm: st33zp24: Fix missing cleanup on get_burstcount() error [ Upstream
Commit: e0ce3da82341fcd6194175f1837946b2a894c625
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0ce3da82341fcd6194175f1837946b2a894c625
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45871
Analysis date: Wed, 27 May 2026 23:46:00 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A st33zp24 TPM send error path can leak an acquired locality when `get_burstcount()` times out, causing local TPM service availability loss.

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

The original Linux kernel CVE announcement for CVE-2026-45871 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45871

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: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-45871	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A cleanup bug in the st33zp24 TPM driver can leave a TPM locality acquired when get_burstcount() fails with a busy or timeout error during st33zp24_send(). This can make later TPM commands fail or hang and cause a TPM service denial of service rather than a kernel memory corruption issue. For the CVSS the PR:L is used because local access to the TPM character device or TPM resource manager may be delegated to a user or service, while full administrator privileges are not inherently required in all deployments. The issue is not network reachable and reliable triggering depends on a TPM busy or timeout condition. Impact is limited to availability of TPM functionality, with no supported evidence of information disclosure, integrity impact, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) 	MAYBE	SIMPLEFIX IMPROVEONLY LINUS 	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

* Local trigger with TPM access: +1
  A local process with access to the TPM character device or TPM resource manager can exercise the send path.

* Availability impact realistic: +1 in paranoid scoring
  If locality is leaked, later TPM operations can fail or hang, causing TPM service DoS.

* Hard device-state condition required: -1
  Reliable triggering depends on `get_burstcount()` returning busy or timeout while locality is held.

* No memory corruption: +0
  This is a missing cleanup path for TPM locality, not UAF, OOB write, double-free, or arbitrary write.

* No remote reachability: +0
  TPM commands are local device operations.

* No confidentiality or integrity impact: +0
  The patch does not indicate key disclosure, TPM authorization bypass, privilege escalation, or policy corruption.

## 3. Reachability analysis

The bug is reachable through local TPM command submission on systems using the `st33zp24` TPM driver. In many systems TPM access may be restricted, but it is commonly mediated through `/dev/tpm*` or `/dev/tpmrm*` and can be delegated to local services.

Namespaces do not normally increase reachability unless TPM devices are passed into containers. The issue is not network reachable. Realistic exploitation requires a timeout or busy condition in `get_burstcount()`.

## 4. Severity interpretation

This behaves like Low or ordinary Moderate availability impact. It can deny TPM functionality, but it does not corrupt kernel memory and does not show privilege escalation or data disclosure. The severity depends mainly on how critical TPM availability is for the product.

## 5. One-sentence report phrase

A st33zp24 TPM send error path can leak an acquired locality when `get_burstcount()` times out, causing local TPM service availability loss.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a local TPM cleanup/resource-state bug with availability-only impact and no memory corruption, remote reachability, or privilege escalation evidence.

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

Patch: tpm: st33zp24: Fix missing cleanup on get_burstcount() error [ Upstream
Commit: e0ce3da82341fcd6194175f1837946b2a894c625
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0ce3da82341fcd6194175f1837946b2a894c625

Changed files:
  drivers/char/tpm/st33zp24/st33zp24.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=e0ce3da82341fcd6194175f1837946b2a894c625

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

The original Linux kernel CVE announcement for CVE-2026-45871 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45871

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).