* [CVE-2026-93818][MODERATE REGULAR] PCI: plda: Protect root bus removal with rescan lock [ Upstream
@ 2026-09-25 0:04 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 0:04 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93818
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: PCI: plda: Protect root bus removal with rescan lock [ Upstream
Commit: 105f212a21cc6bef6855841216dd476022626170
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=105f212a21cc6bef6855841216dd476022626170
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93818
Analysis date: Thu, 24 Sep 2026 20:04:00 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93818 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93818
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: MODERATE REGULAR
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-93818 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93818 CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race condition in the PLDA PCI host controller teardown path can occur because plda_pcie_host_deinit removes a PCI root bus without serializing against concurrent PCI rescan or hotplug operations. A concurrent operation may retain or access PCI root bus objects while they are being stopped and removed, which can result in a use after free condition or a kernel crash. For the CVSS the PR:L in the paranoid score assumes a local actor with delegated PCI hotplug or rescan control such as a service account or a reduced capability administrative context. Direct sysfs control is normally more privileged. The issue is not directly network reachable. Impact is at least local denial of service via kernel crash and in the worst case may allow limited confidentiality or integrity impact due to stale PCI object access. Manual review is needed because the patch identifies a potential use after free but does not demonstrate a controlled reuse or write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES DANGER RACE UAF KERNEL_PANIC_PLUS_UAF LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 Real UAF or active lifetime violation. The patch serializes root bus stop and removal against PCI rescan and hotplug operations. Without this lock, a concurrent operation can access PCI root bus state after teardown may have invalidated it. The commit explicitly identifies possible use after free.
* +1 Reliable kernel crash or strong DoS. The commit explicitly states that the race may cause system crashes.
* +0 Controlled reclaim or controlled replacement. Not demonstrated.
* +0 Arbitrary or directed kernel write. Not demonstrated.
* +0 Structured stale object exploitation leverage. PCI bus objects are structured, but the supplied patch does not show that an attacker controls replacement contents or that a later stale use consumes useful attacker-controlled fields.
* +0 Weak LPE concern. Not awarded merely because a possible UAF exists.
* +0 Local unprivileged trigger. Not established. The complete sequence requires root bus removal together with concurrent rescan or hotplug activity.
* +0 Remote reachability. Not established. The affected operations are PCI management and hotplug control operations, not packet-processing paths.
* +0 Race timing penalty. Not applied. The patch establishes a race, but the supplied evidence does not establish that its timing is unusually narrow, one-shot, or externally uncontrollable.
* +0 host-admin penalty. Not applied because complete privilege requirements for root bus deinitialization and the concurrent operation are not fully shown. Sysfs PCI management commonly requires administrative control, but that is not sufficient evidence to set HostAdminRequired to YES for every possible trigger path.
* No extra Availability point. The same potential crash is already counted by the +1 DoS signal.
* No confidentiality or integrity points. A stale PCI bus reference may theoretically be exploitable, but no disclosure, write, controlled reuse, callback influence, or policy bypass is established.
3. Reachability analysis
The evaluated attacker is a local PCI management or hotplug actor. The vulnerable sequence requires root bus teardown in plda_pcie_host_deinit to overlap with a PCI rescan or hotplug operation.
The commit states that concurrent rescan or hotplug operations can be triggered through sysfs. Direct writes to PCI sysfs management interfaces are commonly restricted to privileged administrative contexts, but the supplied patch does not show the exact capability checks for every required stage. In particular, it does not establish whether an attacker can independently induce PLDA root bus removal, whether removal is triggered by device lifecycle events, or whether a reduced-capability service can drive the complete sequence.
Namespace-scoped reachability is not established. PCI root bus removal concerns a host-owned controller and root bus, and there is no evidence that all required operations can be performed from an attacker-created user or network namespace. No network trigger, prior attacker-controlled firmware state, or special attacker-controlled hardware path is established by the supplied material.
4. Primitive and severity interpretation
The primitive is a concurrent lifetime violation involving PCI root bus teardown and PCI rescan or hotplug traversal. The root bus is an active structured kernel object, but the visible evidence only establishes that it can be accessed during or after removal. It does not establish controlled reclaim, object substitution, stale callback dispatch, refcount takeover, attacker-controlled post-free contents, arbitrary read, arbitrary write, or a security-boundary bypass.
This is not a concrete repeated release or refcount mutation case. The patch adds mutual exclusion around pci_stop_root_bus and pci_remove_root_bus. It does not show an initial release followed by a second put, free, or refcount operation through the same dangling reference.
PrimitiveClass is CLASS_B because the commit directly identifies a possible use after free caused by object lifetime teardown racing with active PCI management operations. The demonstrated practical consequence is kernel crash or local DoS. Exploitation beyond crash remains possible in principle for a lifetime bug, but no patch-supported leverage beyond the stale access is shown.
ImportantCandidate is NO because this is currently a constrained teardown race with no demonstrated reclaim, write primitive, repeatable attacker-controlled lifetime manipulation, or boundary impact. AutoDowngradeAllowed is YES because the current evidence supports a crash-capable but constrained CLASS_B lifetime issue rather than an unresolved active-object corruption primitive with meaningful exploitation leverage. Manual review remains recommended to verify real trigger reachability and whether PLDA root bus teardown can be driven below host-admin privilege in affected products.
5. One-sentence report phrase
A race between PLDA PCI root bus removal and concurrent PCI rescan or hotplug operations may cause use after free access and a local kernel crash, but controlled reuse or a non-DoS exploitation primitive is not established.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm the actual call path to plda_pcie_host_deinit, the privilege requirements for root bus removal and PCI sysfs operations, and whether concurrent rescan or hotplug users can access freed PCI bus objects beyond the documented crash path.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: PCI: plda: Protect root bus removal with rescan lock [ Upstream
Commit: 105f212a21cc6bef6855841216dd476022626170
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=105f212a21cc6bef6855841216dd476022626170
Changed files:
drivers/pci/controller/plda/pcie-plda-host.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=105f212a21cc6bef6855841216dd476022626170
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93818 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93818
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:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS score: 5.8
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: unknown
Paranoid ActionableScore: 3
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: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-09-25 0:04 21% [CVE-2026-93818][MODERATE REGULAR] PCI: plda: Protect root bus removal with rescan lock [ Upstream AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox