* [CVE-2026-80861][LOW] usb: xhci: bail out of setup if the controller is inaccessible
@ 2026-09-04 22:19 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-04 22:19 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80861
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb: xhci: bail out of setup if the controller is inaccessible
Commit: bf84c6b0264947794fa783c324a6d874ca6657d8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf84c6b0264947794fa783c324a6d874ca6657d8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80861
Analysis date: Fri, 04 Sep 2026 18:19:34 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80861 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80861
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-2026-80861 LOW https://www.kernelcve.org/list/?q=CVE-2026-80861 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-754;CWE-703;*CWE-20;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.6';DESCR 'xhci_gen_setup can derive an unaligned operational register pointer when the xHCI controller is inaccessible and the MMIO capability register read returns all ones. The first later access through this pointer can cause an alignment fault on arm64 and crash the kernel during host controller setup. For the CVSS the PR:N is used in the paranoid physical access interpretation because a removable or failing controller may be manipulated without an operating system account. The issue is not network reachable and does not provide a clear memory corruption primitive. Impact is denial of service via kernel oops only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) SKIP CVE-2026-80861 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE READ OOB USB INIT HARDWARE TEST DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap was applied.
2. Signal breakdown
Positive signals:
* +1 Weak or indirect corruption candidate. `xhci->op_regs` can be derived from an invalid MMIO read value and become an unaligned operational register pointer, but this is not a useful attacker controlled corruption primitive.
* +1 Reliable kernel crash or strong DoS. On arm64, the later `readl()` through the unaligned MMIO pointer can fault and produce a kernel Oops during xHCI setup.
Negative signals:
* No negative privilege penalty was applied because host-admin-equivalent privilege is not positively established for all possible scenarios.
* No physical-only or rare-hardware penalty was applied because xHCI controllers are common, although the trigger depends on an inaccessible, failed, or hot-removed controller state.
Important non-awarded signals:
* RealUAF not awarded. No stale lifetime object or post-free use is established.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity impact not awarded.
* Remote reachability not established.
* Extra availability not awarded because the same kernel Oops is already counted once.
* ImportantCandidate not awarded because the patch supports crash-only invalid MMIO access behavior, not memory corruption with unresolved exploitation leverage.
3. Reachability analysis
The vulnerable path is reached during xHCI host controller setup or probe. A local host administrator could potentially exercise related probe, bind, unbind, reset, or power-management paths, but the supplied evidence also describes a device that failed to power up or dropped off the bus.
Below-host-admin software reachability is not established. A physical or hardware-level actor might influence a removable or failing controller state, but this is not direct network reachability and not an ordinary local unprivileged kernel API trigger.
No namespace-scoped privilege path is involved. No prior namespace setup, sysctl, or container capability path is relevant. The issue is architecture-sensitive in practice because arm64 faults on the unaligned device access shown in the report.
Race repeatability is limited to controller accessibility or hot-removal timing, but the score does not subtract a race penalty because the core failure is an invalid setup-time MMIO value handling issue.
4. Primitive and severity interpretation
The exact primitive is invalid derivation of an MMIO operational register pointer from an all-ones capability register read when the controller is inaccessible. The later access becomes an unaligned device-memory read and can crash the kernel on arm64.
This is not an active structured UAF and not fixed stale storage UAF. It is CLASS_C crash or invalid-state behavior. There is no concrete repeated release or refcount operation. There is no evidence of a first lifetime operation freeing an object and a second operation mutating the same dangling reference.
The demonstrated consequence is kernel Oops or DoS during controller setup. Speculative consequences such as privilege escalation, information disclosure, arbitrary write, or controlled memory corruption are not supported by the patch. AutoDowngradeAllowed is YES because no unresolved corruption, ownership, lifetime, or boundary-bypass primitive remains.
Likely operational severity is ordinary Moderate or Low-like DoS, mainly relevant to systems with affected xHCI hardware states and arm64 alignment behavior.
5. One-sentence report phrase
An inaccessible xHCI controller can make setup derive an unaligned operational register pointer from an all ones MMIO read, causing an arm64 kernel Oops during host controller setup and resulting in denial of service only.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: the issue is a hardware access validation bug with crash-only impact and no evidence of UAF, repeated lifetime mutation, OOB write, information disclosure, authorization bypass, or privilege escalation.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: usb: xhci: bail out of setup if the controller is inaccessible
Commit: bf84c6b0264947794fa783c324a6d874ca6657d8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf84c6b0264947794fa783c324a6d874ca6657d8
Commit description:
xhci_gen_setup() locates the operational registers using the capability
length read from the very first register:
xhci->op_regs = hcd->regs +
HC_LENGTH(readl(&xhci->cap_regs->hc_capbase));
If the controller is dead or has dropped off the bus, that read returns
~0, HC_LENGTH() truncates it to 0xff, and op_regs ends up 0xff bytes
past the page-aligned MMIO base, i.e. unaligned. The first access
through it, xhci_halt() -> xhci_handshake() reading op_regs->status, is
then an unaligned readl() on device memory. arm64 faults on unaligned
device accesses, so instead of xhci_handshake() catching the all-ones
value and returning -ENODEV, setup oopses:
xhci-pci-renesas 0005:08:00.0: Unable to change power state from D3cold to D0, device inaccessible
xhci-pci-renesas 0005:08:00.0: xHCI Host Controller
xhci-pci-renesas 0005:08:00.0: new USB bus registered, assigned bus number 1
Unable to handle kernel paging request at virtual address ffff80030a770103
ESR = 0x0000000096000021
FSC = 0x21: alignment fault
Internal error: Oops: 0000000096000021 [#1] SMP
pc : xhci_halt [xhci_hcd]
Call trace:
xhci_halt
xhci_gen_setup
xhci_pci_setup
usb_add_hcd
usb_hcd_pci_probe
xhci_pci_common_probe
xhci_pci_renesas_probe
This was hit with a Renesas uPD720201 that failed to power up ("Unable
to change power state from D3cold to D0, device inaccessible") yet still
reached the HCD probe path.
Read the capability register once, and if it reads back the all-ones
value (as xhci_handshake() and xhci_reset() already test for), abort
setup with -ENODEV before op_regs is derived from it. Reading it once
also avoids re-reading a register that may change under a concurrent
hot-removal.
Fixes: 66d4ead ("USB: xhci: BIOS handoff and HW initialization.")
Cc: [email protected]
Signed-off-by: Breno Leitao <[email protected]>
Signed-off-by: Mathias Nyman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/usb/host/xhci.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=bf84c6b0264947794fa783c324a6d874ca6657d8
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80861 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80861
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:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.6
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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