* [CVE-2026-90178][LOW] hwmon: (coretemp) Fix core_data leak on CPUs without PTS [ Upstream
@ 2026-09-18 5:38 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 5:38 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90178
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: hwmon: (coretemp) Fix core_data leak on CPUs without PTS [ Upstream
Commit: dc0d79b1be384e7f6a2308356afd10dcf3bf940f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc0d79b1be384e7f6a2308356afd10dcf3bf940f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90178
Analysis date: Fri, 18 Sep 2026 01:38:41 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
The coretemp driver leaks the core_data array during device removal on CPUs without PTS, but exploitation requires host-administrative lifecycle control and no memory corruption or immediate host-wide denial of service is established.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90178 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90178
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-2026-90178 LOW https://www.kernelcve.org/list/?q=CVE-2026-90178 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'The coretemp driver can leak the pdata core_data allocation when a device is removed on a CPU without X86_FEATURE_PTS. In this configuration no package temp_data object is created, so the normal package cleanup path does not release the array before the platform data is freed. Repeated driver load and unload or device removal cycles can accumulate kernel memory consumption, although a single cycle leaks only a limited allocation. For the CVSS the PR:H is selected because reliable triggering normally requires administrative control over module loading or coretemp device lifecycle. The issue is not network reachable. Impact is limited to availability through gradual resource exhaustion, with no supported UAF, OOB access, information disclosure, arbitrary write, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) SKIP CVE-2026-90178 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE WARNONLY LEAK HARDWARE - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
## 1. ActionableScore
* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Applied conservative score-range floor: -1 -> 0
* Final recommended bucket: **Ordinary Moderate**::
## 2. Signal breakdown
Conservative signals:
* +1 Concrete persistent kernel resource leak. `pdata->core_data` is allocated and permanently lost when `pdata` is freed on the affected removal path.
* -2 Proven host-admin-equivalent requirement. Repeated module unloading or CPU/device lifecycle control requires host administrative capabilities.
* Raw total: 1 - 2 = -1.
Paranoid signals:
* +1 Concrete persistent kernel resource leak.
* +1 Potential cumulative resource pressure. Repeated load and unload or removal cycles can leak additional allocations, although host-wide exhaustion is not demonstrated.
* -2 Proven host-admin-equivalent requirement.
* Raw total: 1 + 1 - 2 = 0.
Not awarded:
* No UAF, stale dereference, double free, OOB access, or repeated lifetime mutation is established.
* No reliable kernel crash or immediate strong DoS is demonstrated.
* No arbitrary write, controlled reclaim, information disclosure, integrity impact, or privilege escalation is established.
* No remote or ordinary local unprivileged reachability is established.
* No hardware penalty is applied because CPUs without PTS are required, but the supplied evidence does not establish that such hardware is sufficiently rare for a deduction.
* The possible gradual exhaustion is not counted as a second conservative signal because the allocation is limited and substantial system impact requires sustained host-admin activity.
## 3. Reachability analysis
The practical trigger is removal and recreation of the coretemp device, such as repeated module load and unload cycles or relevant CPU/device lifecycle operations. Module unloading requires host-level `CAP_SYS_MODULE`, while CPU hotplug and comparable platform-device management are also host-administrative operations.
These operations are not available through an attacker-created user or network namespace, so the complete trigger is not namespace-scoped. The prerequisite is a CPU without `X86_FEATURE_PTS`, or an equivalent environment that reaches the same no-package-data path. No network input, race, special timing, or attacker-controlled memory payload is involved.
## 4. Primitive and severity interpretation
The exact defect is a missing `kfree()` that causes an allocated pointer array to become unreachable when its owning `platform_data` is freed. This is a concrete resource leak, classified as CWE-401 and CWE-772, but not a memory-corruption primitive.
There is no post-lifetime access to `core_data`. The new `kfree()` is safe on PTS-capable systems because the existing package cleanup path sets the pointer to `NULL`. The demonstrated consequence is limited kernel-memory loss per affected device-removal cycle. Gradual resource exhaustion is theoretically possible through sustained repetition, but the supplied evidence does not show immediate or practical host-wide failure.
`PrimitiveClass=NONE` because no corruption, stale-object use, authorization bypass, ownership violation, or equivalent security primitive exists. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` because the issue is a small host-admin-triggered leak with no unresolved exploitation leverage.
## 5. One-sentence report phrase
The coretemp driver leaks the core_data array during device removal on CPUs without PTS, but exploitation requires host-administrative lifecycle control and no memory corruption or immediate host-wide denial of service is established.
## 6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch fixes a straightforward, bounded-per-cycle resource leak with a host-admin trigger and no corruption, disclosure, boundary bypass, or privilege-escalation primitive.
## 7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: hwmon: (coretemp) Fix core_data leak on CPUs without PTS [ Upstream
Commit: dc0d79b1be384e7f6a2308356afd10dcf3bf940f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc0d79b1be384e7f6a2308356afd10dcf3bf940f
Changed files:
drivers/hwmon/coretemp.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=dc0d79b1be384e7f6a2308356afd10dcf3bf940f
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90178 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90178
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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.4
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: unknown
Paranoid ActionableScore: 0
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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