* [CVE-2026-98758][MODERATE 7.0] usb: typec: ucsi: glink: fix use-after-free of ucsi on remove
@ 2026-10-24 16:58 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 16:58 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98758
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: usb: typec: ucsi: glink: fix use-after-free of ucsi on remove
Commit: 432b58cd959e594909a581b4974396cdbc9d4ca1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=432b58cd959e594909a581b4974396cdbc9d4ca1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98758
Analysis date: Sat, 24 Oct 2026 12:58:29 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
A teardown race permits PMIC Glink work to access connector state freed by `ucsi_unregister()`, plausibly crashing the kernel without a demonstrated controlled-reuse or privilege-escalation primitive.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98758 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98758
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-2026-98758 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98758 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=5 LEGACY=MODERATE_KPANIC RESULT=SAME (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-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A teardown race in the PMIC Glink UCSI driver allows notification callbacks to queue notify_work or register_work after pmic_glink_ucsi_remove starts but before devres releases the pmic_glink client. Work running after ucsi_unregister can access the freed connector array or register and unregister the UCSI instance again. The demonstrated primitive is a kernel use after free with duplicate lifecycle operations and the most direct impact is a local kernel crash. Reliable triggering requires a callback to overlap device removal or driver unbind, so AC:H is appropriate. For the CVSS the PR:L value is used in the paranoid vector because delegated device management or a reduced capability service may be able to initiate teardown while influencing Type C events, although ordinary unprivileged users normally cannot remove this device. The freed state may be accessed and modified by asynchronous work, so memory corruption and privilege escalation require manual investigation even though no controlled write or proven escalation path is established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 5 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE USB INIT UAF LINUS KPANIC - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 2.
* Conservative score: 4. REAL UAF FLOOR 4 applies because asynchronous work consumes freed structured connector state and host-admin-only reachability is not established.
* Raw paranoid score: 2.
* Paranoid score: 4. No additional exploit primitive is sufficiently supported.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 — Real UAF: `ucsi_unregister()` frees the connector array while callbacks can still queue work that later dereferences it.
* +1 — Plausible kernel crash/DoS from post-free connector access or duplicate lifecycle processing.
* -1 — Narrow teardown timing: a callback/work item must overlap device removal before devres releases the PMIC Glink client.
* No repeated-release +1: the patch mentions a second unregister, but does not show that the first unregister ends the `struct ucsi` lifetime or that an exact dangling lifetime reference receives a second refcount/free mutation.
* No structured-leverage point: attacker-controlled reclaim, replacement contents, pointer consumption, or another useful post-reuse operation is not shown.
* No C/I, arbitrary write, controlled reclaim, LPE, or extra availability point is awarded.
* NEW52 B5-R and NEW53 B3-PENDING do not apply; no retry-accumulated OOB or shared-backing write is shown.
3. Reachability analysis
The complete trigger requires device teardown/unbind plus a PMIC Glink notification during the teardown window. The patch does not establish whether an ordinary user, delegated device-management service, or only a host administrator can initiate removal and influence the callback. Namespace capability scope and prior delegation are likewise unknown. Relevant Qualcomm PMIC Glink hardware is required, but physical attacker access is not shown. The timing appears one-shot and teardown-specific rather than cheaply repeatable.
4. Primitive and severity reading
This is an active structured-state UAF, not fixed stale storage: queued work consumes connector state freed by unregister. It occurs specifically during removal and may also cause duplicate registration/unregistration, but the supplied code does not prove a concrete second lifetime mutation through an already-freed `struct ucsi`. Thus it is CLASS_B with crash/DoS supported and stronger corruption effects unresolved. The cleanup-bound scope, uncertain attacker reachability, and absence of material reuse leverage make it unsuitable as an Important candidate on current evidence; automatic Moderate handling remains permissible, but review is advisable.
There is no authorization decision or protected-resource bypass, so B4 pending review is inapplicable.
5. One-sentence report phrase
A teardown race permits PMIC Glink work to access connector state freed by `ucsi_unregister()`, plausibly crashing the kernel without a demonstrated controlled-reuse or privilege-escalation primitive.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm removal permissions, callback influence, and whether either work item performs writes or duplicate frees against reclaimed connector state.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: usb: typec: ucsi: glink: fix use-after-free of ucsi on remove
Commit: 432b58cd959e594909a581b4974396cdbc9d4ca1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=432b58cd959e594909a581b4974396cdbc9d4ca1
Commit description:
The pmic_glink client is released by the devres cleanup, which runs
after pmic_glink_ucsi_remove() has returned, so its notification
callbacks can queue work until then. Work that runs after
ucsi_unregister() has been called touches freed state: it dereferences
the connector array that ucsi_unregister() freed, or registers and
unregisters the instance a second time.
Disable both work items with disable_work_sync() before unregistering,
and unregister only if the instance is still registered.
This issue was found by an in-house static analysis tool.
Fixes: 62b5412 ("usb: typec: ucsi: add PMIC Glink UCSI driver")
Cc: stable <[email protected]>
Assisted-by: Codex:gpt-5.6
Link: https://lore.kernel.org/r/[email protected]
Co-developed-by: Song Li <[email protected]>
Signed-off-by: Song Li <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
Reviewed-by: Heikki Krogerus <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/usb/typec/ucsi/ucsi_glink.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=432b58cd959e594909a581b4974396cdbc9d4ca1
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98758 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98758
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: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: 4
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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