* [CVE-2026-98677][MODERATE 7.0] iio: adc: ad_sigma_delta: fix use-after-free on unbind [ Upstream
@ 2026-10-24 14:23 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 14:23 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98677
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: iio: adc: ad_sigma_delta: fix use-after-free on unbind [ Upstream
Commit: 84500ae0d976995a6870cb1dca2d124b6b2d6e5a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=84500ae0d976995a6870cb1dca2d124b6b2d6e5a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98677
Analysis date: Sat, 24 Oct 2026 10:23:29 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: YES
Summary:
Host driver unbind can race an enabled ADC IRQ, allowing the trigger handler to copy samples into a devm-freed heap buffer and potentially crash the kernel.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98677 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98677
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 7.0
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-2026-98677 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98677 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=5 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An incorrect devres allocation order creates a kernel heap use after free during driver unbind. samples_buf is freed before iio_device_unregister disables the triggered buffer and free_irq drains the data ready handler, so ad_sd_trigger_handler can execute memcpy into freed memory. This is a concrete stale pointer write rather than a NULL dereference or resource leak. It can cause a kernel crash, and reuse of the freed allocation as another kernel object could produce confidentiality or integrity impact. Controlled privilege escalation is not demonstrated and depends on heap reuse, interrupt timing, and influence over ADC sample bytes. For the CVSS the PR:H base value reflects that direct driver unbind normally requires administrative access. For the CVSS the PR:L paranoid value reflects deployments where a local service account, delegated device manager, or reduced capability process can control IIO operation or device lifecycle actions. The issue is local and is not directly network reachable. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 1.6 and ActionableScore 5 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE NOMEMCHK UAF HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=REQUIRED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 1.
* Conservative score: 1; no floor applies because host-admin-equivalent driver unbind is required.
* Raw paranoid score: 1.
* Paranoid score: 1; generic heap reuse does not justify another point.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +2 Real UAF: reverse devres release frees `samples_buf` while the IRQ-triggered handler can still use it.
* +1 Reliable kernel crash/strong DoS: `ad_sd_trigger_handler()` performs `memcpy()` into freed heap storage.
* -2 Host-admin-equivalent prerequisite: the evidenced trigger is driver unbind, ordinarily controlled through the host driver-management interface.
* No separate overwrite point: the stale `memcpy()` is the operation establishing the UAF, so counting both would duplicate one primitive.
* No race penalty: interrupt timing is required, but the evidence does not establish a particularly narrow or irreproducible race.
* Controlled reclaim, chosen target, attacker-controlled sample bytes, arbitrary write, disclosure, LPE, and protected-state corruption are not shown.
* No additional availability point is awarded for the same possible crash.
* NEW52/B5-R does not apply: there is no retry-accumulated index or confirmed OOB mechanism.
* NEW53/B3-PENDING and NEW54/B4-PENDING do not apply.
3. Reachability analysis
The demonstrated lifecycle transition is host driver unbind while a data-ready IRQ remains active. Normal local users, namespace capabilities, delegated IIO access, or render-node-like interfaces are not shown to permit the complete unbind sequence. The legacy delegated-service scenario is hypothetical rather than patch-proven. No network path exists. Applicable hardware and an interrupt in the teardown window are required; no separate rare-hardware penalty is justified.
4. Primitive and severity reading
This is a real fixed-storage asynchronous UAF write: the stale pointer names the former sample buffer, and the IRQ handler copies device sample data to that address. It is CLASS_B rather than CLASS_A because controlled reclaim, target selection, payload control, or corruption of a named replacement object is absent. The shown effect is heap corruption with plausible crash; corruption of a useful reclaimed object remains theoretical.
This is not a repeated-release/refcount case: there is no first lifetime release followed by a second lifetime mutation through the same reference. ImportantCandidate is therefore NO. AutoDowngradeAllowed is YES under the constrained fixed-stale-buffer profile, although the supplied triage direction warrants mandatory human confirmation.
5. One-sentence report phrase
Host driver unbind can race an enabled ADC IRQ, allowing the trigger handler to copy samples into a devm-freed heap buffer and potentially crash the kernel.
6. Manual review advice
MANUAL CHECK REQUIRED
Confirm whether product-specific device-management delegation permits a below-host-admin actor to initiate unbind or equivalent teardown.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: iio: adc: ad_sigma_delta: fix use-after-free on unbind [ Upstream
Commit: 84500ae0d976995a6870cb1dca2d124b6b2d6e5a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=84500ae0d976995a6870cb1dca2d124b6b2d6e5a
Changed files:
drivers/iio/adc/ad_sigma_delta.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=84500ae0d976995a6870cb1dca2d124b6b2d6e5a
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98677 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98677
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:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
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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