[CVE-2026-53121][LOW] amd-pstate: Fix memory leak in amd_pstate_epp_cpu_init() [ Upstream

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

CVE: CVE-2026-53121
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: amd-pstate: Fix memory leak in amd_pstate_epp_cpu_init() [ Upstream
Commit: 539aabbab190825c77eb455ec35652cb3720625f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=539aabbab190825c77eb455ec35652cb3720625f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53121
Analysis date: Mon, 06 Jul 2026 19:42:44 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A privileged local actor who can repeatedly trigger AMD P-state EPP initialization failures may cause a small kernel memory leak in `amd_pstate_epp_cpu_init()`, potentially leading to resource-exhaustion DoS only under sustained abuse.

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

The original Linux kernel CVE announcement for CVE-2026-53121 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53121

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53121	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'A memory leak exists in amd_pstate_epp_cpu_init() when setting the EPP value fails after cpudata has already been allocated. The function returns the error directly and leaves the cpudata allocation unreleased, so repeated failed initialization attempts could gradually consume kernel memory. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over cpufreq driver initialization, CPU hotplug, or related system power management operations. The issue is not network reachable and does not provide an evident memory corruption primitive. Impact is denial of service through resource exhaustion only, with no supported path to information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	YES	LEAK UAF HARDWARE 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered signals:

* Availability impact realistic: +1, paranoid only. Repeated failed initialization could leak kernel memory over time, but this requires sustained repetition and is not an immediate crash primitive.
* Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering normally requires privileged control over cpufreq driver initialization, CPU hotplug, module or platform power-management state.

Not triggered:

* No remote/network reachability.
* No local unprivileged trigger.
* No UAF, double free, OOB write, type confusion, refcount abuse, stale callback, or arbitrary write.
* No confidentiality or integrity impact.
* No practical privilege escalation path.
* No strong DoS signal, because the leak is small, error-path dependent, and not shown to cause immediate system-wide failure.

## 3. Reachability analysis

The affected path is `amd_pstate_epp_cpu_init()` in the AMD P-state cpufreq driver. The bug is reached only when `amd_pstate_set_epp()` fails after `cpudata` allocation. In normal deployments, causing repeated CPU policy initialization failures requires administrative control over CPU frequency management, CPU hotplug, driver loading, or related system configuration. Namespaces or containers generally do not make this reachable to an unprivileged user unless the host has delegated unusually broad power-management controls, which is not typical. The path is not network reachable.

Call-site confidence: medium. The diff shows the error path and cleanup target, but not the full function body or all driver lifecycle callers.

## 4. Severity interpretation

This behaves like a low-risk resource leak, not an Important-class kernel vulnerability. Theoretical worst case is gradual kernel memory exhaustion after repeated privileged failed initialization attempts. Realistic exploitation evidence is weak because the bug is an error-path leak with high privilege requirements and no memory corruption primitive.

## 5. One-sentence report phrase

A privileged local actor who can repeatedly trigger AMD P-state EPP initialization failures may cause a small kernel memory leak in `amd_pstate_epp_cpu_init()`, potentially leading to resource-exhaustion DoS only under sustained abuse.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED.

This can be auto-closed or deferred in most triage pipelines because it is a privileged error-path memory leak without UAF, OOB access, arbitrary write, privilege escalation, information disclosure, or network exposure.

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

Patch: amd-pstate: Fix memory leak in amd_pstate_epp_cpu_init() [ Upstream
Commit: 539aabbab190825c77eb455ec35652cb3720625f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=539aabbab190825c77eb455ec35652cb3720625f

Changed files:
  drivers/cpufreq/amd-pstate.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=539aabbab190825c77eb455ec35652cb3720625f

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

The original Linux kernel CVE announcement for CVE-2026-53121 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53121

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.1

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: 0
  Paranoid ActionableScore: 1

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).