* [CVE-2026-97905][LOW] cpufreq: zero-initialize policy cpumask before sysfs publication
@ 2026-09-25 17:40 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 17:40 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97905
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: cpufreq: zero-initialize policy cpumask before sysfs publication
Commit: 0de2f3918fbbbb767e7e716178194b66560dd12a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0de2f3918fbbbb767e7e716178194b66560dd12a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97905
Analysis date: Fri, 25 Sep 2026 13:40:32 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
An uninitialized cpufreq policy cpumask can be exposed through sysfs before policy initialization completes, potentially allowing sysfs callbacks to run on a partially initialized policy, but the supplied patch does not establish memory corruption, privilege escalation, or a reliable kernel crash.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97905 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97905
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-2026-97905 LOW https://www.kernelcve.org/list/?q=CVE-2026-97905 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:L/UI:N/S:U/C:N/I:N/A:L';CWE-908;CWE-665;CWE-362;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'An uninitialized cpufreq policy cpumask can be published through sysfs before cpufreq policy initialization is complete. If the uninitialized bitmap is nonzero, policy_is_inactive may treat the policy as active and allow sysfs show or store callbacks to run on a partially initialized policy. This is a local timing issue during CPU policy creation or CPU online processing and is not network reachable. For the CVSS the PR:L paranoid value assumes an unprivileged local process can race sysfs access with a policy creation event initiated by another component. In typical deployments reliably forcing CPU hotplug or cpufreq policy creation requires administrative control. The patch context does not demonstrate a use-after-free, out-of-bounds access, arbitrary write, information disclosure of meaningful kernel data, or privilege escalation. Impact is expected to be limited to incorrect sysfs handling or limited denial of service.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES HARDWARE NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
## 1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap was applied.
## 2. Signal breakdown
* +1 Weak invalid-state exposure. The policy cpumask is published through sysfs before it receives its first valid value. A nonzero uninitialized bitmap can bypass policy_is_inactive and allow sysfs callbacks to operate on a partially initialized cpufreq policy.
No additional signals awarded:
* No UAF, stale post-free reference, double free, or refcount mutation is established.
* No OOB read or write is established.
* No arbitrary write, controlled reclaim, callback control, or object replacement is established.
* No meaningful kernel information disclosure is established. The uninitialized allocation is a cpumask bitmap, and the supplied patch does not show sensitive bytes copied to userspace.
* No reliable kernel crash, panic, or host-wide DoS is demonstrated.
* No integrity impact, privilege escalation, authorization bypass, or security-boundary violation is demonstrated.
* No remote reachability is established.
* No Local unprivileged trigger point is awarded because the supplied context does not establish that an unprivileged actor can cause cpufreq policy creation or CPU online processing.
* No hard-race penalty is applied. The patch establishes a publication-before-initialization window, but does not establish an unusually narrow or externally uncontrollable timing condition.
## 3. Reachability analysis
The vulnerable observation point is local sysfs access to a cpufreq policy directory after kobject publication and before cpufreq_policy_online assigns a valid policy cpumask.
The complete trigger sequence is not established for an ordinary local user. Reading some cpufreq sysfs attributes may be available to non-administrative users, but reliably creating the vulnerable window may require CPU online processing, driver registration, CPU hotplug activity, or another policy creation event. The supplied patch does not establish which actor can initiate that sequence.
Host-admin-equivalent privilege is therefore UNKNOWN rather than YES. Below-host-admin reachability is also not established for the complete sequence, so HostAdminRequired is not NO.
No namespace-scoped capability analysis is supported by the supplied context. No network namespace, user namespace, delegated capability, prior host provisioning, special hardware, sysctl, or boot-option prerequisite is established.
The issue is not network reachable. Repeatability is unresolved because the supplied patch does not show a user-controlled way to repeatedly create cpufreq policies while concurrently accessing their sysfs attributes.
## 4. Primitive and severity interpretation
The established primitive is publication of an incompletely initialized cpufreq policy object. The uninitialized policy cpumask can be nonempty because alloc_cpumask_var does not zero the separate allocation when CONFIG_CPUMASK_OFFSTACK is enabled.
This causes a logic and initialization failure. policy_is_inactive can return false before policy initialization completes, allowing show or store callbacks to run too early.
This is not a UAF. No object is freed while a stale reference remains in use. No second release, put, free, or refcount operation exists. No active structured stale-object lifetime primitive is established.
The demonstrated risk is invalid sysfs callback execution against a partially initialized policy. The patch does not establish that any reachable callback dereferences a NULL field, performs an unsafe write, leaks meaningful data, corrupts memory, or crosses a security boundary.
PrimitiveClass is NONE because no meaningful corruption, ownership, authorization, or lifetime primitive is directly established. ImportantCandidate is NO because the evidence supports an initialization-order defect with limited and unresolved practical impact, not an Important-grade exploitation primitive.
AutoDowngradeAllowed is YES because no concrete unresolved kernel corruption primitive, UAF, authorization bypass, shared ownership violation, or meaningful post-lifetime mutation remains.
Likely operational severity is Low-like or ordinary Moderate. Review is still useful to inspect the actual cpufreq sysfs callbacks reachable before cpufreq_policy_online completes and determine whether any callback has stronger assumptions about initialized policy fields.
## 5. One-sentence report phrase
An uninitialized cpufreq policy cpumask can be exposed through sysfs before policy initialization completes, potentially allowing sysfs callbacks to run on a partially initialized policy, but the supplied patch does not establish memory corruption, privilege escalation, or a reliable kernel crash.
## 6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The exact reachable cpufreq sysfs show and store callbacks were not supplied, so manual inspection should verify whether any callback can cause a NULL dereference, unsafe state update, or meaningful information exposure during the publication window.
## 7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: cpufreq: zero-initialize policy cpumask before sysfs publication
Commit: 0de2f3918fbbbb767e7e716178194b66560dd12a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0de2f3918fbbbb767e7e716178194b66560dd12a
Commit description:
cpufreq_policy_alloc() allocates policy->cpus with alloc_cpumask_var(),
i.e. without __GFP_ZERO, unlike the sibling related_cpus and real_cpus
masks. With CONFIG_CPUMASK_OFFSTACK=y the mask is a separate
kmalloc_node() allocation, so its bitmap holds whatever the slab allocator
left behind:
cpufreq_online()
cpufreq_policy_alloc()
alloc_cpumask_var(&policy->cpus) /* bitmap is uninitialized */
kobject_init_and_add() /* policy%u/ appears in sysfs */
cpufreq_policy_online()
cpumask_copy(policy->cpus, cpumask_of(cpu)) /* first valid value */
This leaves a window in which the sysfs attributes are already reachable
while policy->cpus is still garbage. show()/store() gate on
policy_is_inactive(), i.e. cpumask_empty(policy->cpus), so a non-zero
bitmap makes them run the attribute callbacks on a policy that is not
initialized yet.
Fix this by using zalloc_cpumask_var() for policy->cpus.
Fixes: 2fc3384 ("cpufreq: Initialize policy->kobj while allocating policy")
Cc: All applicable <[email protected]>
Signed-off-by: Zhongqiu Han <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Rafael J. Wysocki <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/cpufreq/cpufreq.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=0de2f3918fbbbb767e7e716178194b66560dd12a
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97905 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97905
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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 3.3
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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