* [CVE-2026-90129][LOW] virtio_balloon: quiesce balloon work before device shutdown [ Upstream
@ 2026-09-17 18:55 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-17 18:55 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90129
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: virtio_balloon: quiesce balloon work before device shutdown [ Upstream
Commit: 6dd28e32f4d81a0d57c732b9900de24184e60a7d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6dd28e32f4d81a0d57c732b9900de24184e60a7d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90129
Analysis date: Thu, 17 Sep 2026 14:55:36 -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-2026-90129 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90129
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-2026-90129 LOW https://www.kernelcve.org/list/?q=CVE-2026-90129 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-664;CWE-404;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'virtio_balloon can continue asynchronous balloon work after the generic virtio shutdown path has broken and reset the device. This can turn a normal reboot or kexec based upgrade into a guest kernel panic when WARN_ON_ONCE() is reached with panic_on_warn enabled, or into a shutdown hang when inflate/deflate or OOM paths wait on a queue that can no longer complete. For the CVSS the PR:L in the paranoid score reflects environments where a delegated service account or reduced capability administrator can initiate reboot or kexec operations. The issue is not network reachable and is triggered through local device lifecycle control during shutdown rather than packet or guest workload input. Impact is denial of service of the guest system only, with no supported evidence of memory corruption, information disclosure, privilege escalation, or guest to host escape.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES VIRT INIT WARNONLY HARDWARE LINUS BOOT INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO 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 changed the score.
2. Signal breakdown
Positive signals:
* +1 Reliable kernel crash / strong DoS: the commit explicitly describes WARN_ON_ONCE() becoming a fatal panic when panic_on_warn is enabled during reboot or kexec.
* +1 Distinct shutdown availability failure: the inflate/deflate and OOM paths may block forever in wait_event() on a broken virtqueue, which is a distinct shutdown hang mechanism beyond the WARN path.
Negative or non-awarded signals:
* Real UAF not awarded: shutdown does not free the virtio_balloon object, and the patch quiesces work before device reset rather than fixing post-free object use.
* Memory corruption not awarded: no UAF, OOB access, double free, refcount corruption, arbitrary write, or controlled stale object reuse is established.
* C/I impact not awarded: the established effects are panic or hang only.
* Remote reachability not awarded: the trigger is device shutdown during reboot or kexec, not network input.
* Local unprivileged trigger not awarded: ordinary unprivileged reachability is not established.
* Strong LPE or weak LPE not awarded: no privilege escalation primitive is supported.
* Extra availability beyond the two distinct shutdown failure modes not awarded.
* Concrete repeated release/refcount not awarded: there is no first release ending lifetime followed by a second lifetime mutation through the same dangling reference.
* Structured stale-object leverage not awarded: asynchronous work touches a broken device state, but no exploitable stale structured object consumption is shown.
3. Reachability analysis
The vulnerable condition occurs during device_shutdown(), typically on reboot or kexec. Directly initiating reboot or kexec usually requires privileged system control such as CAP_SYS_BOOT or an administrator-managed update path, but the supplied evidence does not fully resolve whether a delegated service account or policy-controlled local user could initiate the complete path in a given deployment. Therefore HostAdminRequired is UNKNOWN rather than YES or NO.
The issue is not namespace scoped. No evidence shows that an attacker-created namespace can perform the complete shutdown or kexec trigger. No network trigger is established. The vulnerable feature requires a virtio_balloon device, so it mainly affects virtualized systems using virtio ballooning, but this is common enough that no rare-hardware penalty is applied. There is no race requiring attacker timing control.
4. Primitive and severity interpretation
The exact primitive is an invalid device lifecycle ordering: virtio_balloon asynchronous work remains armed while the generic virtio shutdown path breaks and resets the device. The demonstrated consequences are a fatal WARN under panic_on_warn or an indefinite wait on a virtqueue that can no longer complete.
This is not active structured UAF and not fixed stale freed storage. It is a shutdown quiescing bug with crash/hang behavior. PrimitiveClass is CLASS_C because the behavior is primarily DoS/invalid-state without an independently useful corruption primitive.
ImportantCandidate is NO because no memory corruption, authorization bypass, guest-to-host escape, information disclosure, integrity impact, or privilege escalation path is established. AutoDowngradeAllowed is YES because the issue is a constrained shutdown-path DoS and no unresolved strong primitive would be lost by treating it as ordinary Moderate/Low-like.
Likely operational severity is ordinary Moderate, mainly relevant to systems using virtio_balloon where reboot or kexec based upgrades may fail.
5. One-sentence report phrase
virtio_balloon asynchronous work may remain active after the generic virtio shutdown path breaks and resets the device, allowing reboot or kexec to trigger a guest kernel panic with panic_on_warn or a shutdown hang, with impact limited to denial of service.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: this is a shutdown path DoS with no established UAF, memory corruption, authorization bypass, privilege escalation, or network reachability.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: virtio_balloon: quiesce balloon work before device shutdown [ Upstream
Commit: 6dd28e32f4d81a0d57c732b9900de24184e60a7d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6dd28e32f4d81a0d57c732b9900de24184e60a7d
Changed files:
drivers/virtio/virtio_balloon.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=6dd28e32f4d81a0d57c732b9900de24184e60a7d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90129 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90129
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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.5
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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