* [CVE-2026-98820][LOW] blk-mq: set RQF_USE_SCHED when the operation is known [ Upstream
@ 2026-10-24 6:59 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-24 6:59 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98820
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: blk-mq: set RQF_USE_SCHED when the operation is known [ Upstream
Commit: 790730e4d95de8356a573d4b4864486bba731863
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=790730e4d95de8356a573d4b4864486bba731863
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98820
Analysis date: Sat, 24 Oct 2026 02:59:10 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
Cached blk-mq requests reused across passthrough and scheduled I/O can skip scheduler initialization and completion pairing, leaking Kyber tokens until the block queue stalls.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98820 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98820
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-2026-98820 LOW https://www.kernelcve.org/list/?q=CVE-2026-98820 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;**CWE-400;CWE-404;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A cached blk mq request allocated for a passthrough operation can later be reused for normal read or write IO without RQF_USE_SCHED. The request may enter the IO scheduler without prepare_request and be freed without finish_request, allowing Kyber to leak a domain token acquired at dispatch and eventually stall the affected block queue. For the CVSS the PR:L value reflects that reliable triggering requires local access to issue the relevant block IO and passthrough operations. No UAF, OOB access, information leak, or write primitive is indicated, so confidentiality and integrity remain unaffected. Availability impact can become high when repeated token leakage stalls a queue serving critical storage, but host wide failure is deployment dependent. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. 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. The independent weaker Aegis shadow evaluated CVSS 2.6 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE INIT LEAK - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 2.
* Conservative score: 2; no floor or cap applied.
* Raw paranoid score: 2.
* Paranoid score: 2; no technically supported stronger primitive.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel resource leak: a reused request can enter Kyber without `prepare_request()`/`finish_request()` pairing, leaking the domain token acquired at dispatch.
* +1 Strong DoS: accumulated token loss can stall the affected block queue.
* No additional availability point: queue stalling is the same consequence already counted.
* No UAF, OOB read/write, arbitrary write, shared-backing write, or corrupted active-state consumer is shown.
* NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write.
* No authorization decision changes from DENY to ALLOW; B4-PENDING does not apply.
* No confidentiality or integrity impact is evidenced.
3. Reachability analysis
The actor must issue a sequence involving passthrough and ordinary read/write operations so cached requests cross operation types. The evidence does not establish whether the complete sequence is available to an ordinary user, a delegated storage service, or only an actor with host-level block-device privileges. Therefore host-admin and UID-0 requirements remain unknown, and no local-unprivileged bonus or privilege penalty is applied. No namespace-scoped capability path, special hardware, or timing race is shown. Repetition appears necessary to exhaust Kyber tokens, but this does not constitute a hard-race penalty.
4. Primitive and severity reading
The primitive is a request-initialization/cleanup mismatch causing a persistent scheduler-domain token leak. It is not a lifetime UAF or memory-corruption primitive. The later effect is consumption of available Kyber tokens until queue progress stalls, making this CLASS_C availability/resource-state behavior. No useful leverage remains beyond resource loss and queue denial of service. ImportantCandidate is therefore NO, and automatic downgrade is allowed.
5. One-sentence report phrase
Cached blk-mq requests reused across passthrough and scheduled I/O can skip scheduler initialization and completion pairing, leaking Kyber tokens until the block queue stalls.
6. Manual review advice
NO MANUAL CHECK NEEDED
The patch supports a bounded resource-management and availability issue without memory corruption, authorization bypass, or unresolved cross-boundary integrity impact.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: blk-mq: set RQF_USE_SCHED when the operation is known [ Upstream
Commit: 790730e4d95de8356a573d4b4864486bba731863
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=790730e4d95de8356a573d4b4864486bba731863
Changed files:
block/20260916151655.2588-1-15815827059
block/blk-mq.c
block/mq-deadline.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=790730e4d95de8356a573d4b4864486bba731863
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98820 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98820
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:L/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.7
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: 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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