* [CVE-2026-98652][MODERATE 7.0] KVM: s390: Add missing srcu in kvm_s390_set_irq_state() [ Upstream
@ 2026-10-24 17:27 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 17:27 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98652
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: KVM: s390: Add missing srcu in kvm_s390_set_irq_state() [ Upstream
Commit: 7a33007b95c8908ae3980eb2b4c508f8936766df
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7a33007b95c8908ae3980eb2b4c508f8936766df
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98652
Analysis date: Sat, 24 Oct 2026 13:27:28 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A VMM can race s390 Store Status with KVM memory-slot replacement, allowing host kernel code to consume stale slot state without SRCU protection.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98652 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98652
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-2026-98652 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98652 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 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-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in kvm_s390_set_irq_state can execute the Store Status operation lacking kvm srcu protection while another VMM thread replaces or removes KVM memory slots. This can allow kvm_s390_store_status_unloaded to observe stale slot state and creates a plausible use after free candidate in the host kernel, although the patch does not establish a controlled write or proven privilege escalation primitive. For the CVSS the PR:L value reflects that the attacker needs local access to the VM or VCPU file descriptor and must invoke KVM control operations. AC:H reflects the need to race Store Status against memory slot modification. The base impact is host denial of service, while the paranoid score accounts for possible host confidentiality and integrity impact if stale memory slot access becomes exploitable. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because KP specialist did not establish a qualifying panic. 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. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 0 with primitive class NONE 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 Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE DANGER VIRT SIMPLEFIX HARDWARE LINUS KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 4.
* Conservative score: 4; no floor or cap changed the result.
* Raw paranoid score: 5.
* Paranoid score: 5; the extra point reflects defensible active structured-state consumption, not assumed guest escape or arbitrary write.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 — Real lifetime violation: Store Status traverses/uses KVM memory-slot state without the SRCU or slots lock required to keep that state alive during concurrent slot removal or replacement.
* +1 — Attacker-influenced lifetime sequence: a VM/VCPU-fd-holding VMM process can invoke Store Status while another VMM thread changes memory slots.
* +1 — Plausible host-kernel crash/DoS from stale slot-state consumption.
* Paranoid +1 — Store Status uses the stale structured slot state for an actual guest-memory operation, materially affecting address/mapping selection rather than merely inspecting diagnostic metadata.
* No race penalty: concurrency is required, but the evidence does not establish a narrow, one-shot, or externally uncontrollable race.
* No controlled reclaim, attacker-shaped replacement object, arbitrary host write, disclosure, LPE, or guest escape is shown. No additional availability or C/I points were awarded.
3. Reachability analysis
The supported attacker is a local VMM process holding the relevant VM/VCPU file descriptors, not guest code alone. That process can invoke IRQ-state restoration and, with VM-fd authority, drive memory-slot replacement/removal from another thread. The evidence characterizes this as below-host-admin fd-scoped privilege and does not require host UID 0. No namespace capability is involved. Guest-only triggering and host-administrator involvement are not shown. No special race unreliability beyond concurrent VMM operations is established.
4. Primitive and severity reading
This is an active structured-state SRCU lifetime violation: stale KVM memory-slot state may be consumed by `kvm_s390_store_status_unloaded()`. It is CLASS_B, not CLASS_A, because controlled reuse or directed host-memory corruption is unproven. The shown/credible effect is host crash; non-crash leverage through stale mapping consumption remains unresolved. The specific below-host-admin VMM-to-host boundary plus active stale-state consumption makes it an Important review candidate under V33, without proving Important severity. Auto-downgrade is unsafe until the exact stale slot fields, resulting write destination, and behavior after slot replacement are reviewed.
5. One-sentence report phrase
A VMM can race s390 Store Status with KVM memory-slot replacement, allowing host kernel code to consume stale slot state without SRCU protection.
6. Manual review advice
MANUAL CHECK REQUIRED
Determine whether stale slot lookup can redirect or extend the Store Status memory write beyond the retired userspace mapping, rather than only causing a host fault.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: KVM: s390: Add missing srcu in kvm_s390_set_irq_state() [ Upstream
Commit: 7a33007b95c8908ae3980eb2b4c508f8936766df
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7a33007b95c8908ae3980eb2b4c508f8936766df
Changed files:
arch/s390/kvm/interrupt.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=7a33007b95c8908ae3980eb2b4c508f8936766df
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98652 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98652
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: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: 4
Paranoid ActionableScore: 5
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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