* [CVE-2026-97990][MODERATE 7.0] vdpa_sim_net: check TX pull result before RX copy [ Upstream
@ 2026-09-25 17:32 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 17:32 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97990
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: vdpa_sim_net: check TX pull result before RX copy [ Upstream
Commit: c001abcde865b74231da8f1412c3217dbf66781e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c001abcde865b74231da8f1412c3217dbf66781e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97990
Analysis date: Fri, 25 Sep 2026 13:32:47 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97990 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97990
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-2026-97990 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97990 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H';CWE-195;CWE-681;CWE-125;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7.1';DESCR 'A signed error result from vringh_iov_pull_iotlb can be used as an unsigned length in the vdpa_sim_net TX to RX path. A negative pull result can therefore become a very large size_t value and can cause receive_filter and vringh_iov_push_iotlb to read beyond the PAGE_SIZE net buffer. This may crash the host kernel and may copy unintended host memory into a guest controlled RX buffer. For the CVSS the PR:L is used because reliable triggering requires a local user or guest context that can control a vDPA virtqueue or an assigned virtual device. The issue is not directly network reachable from an external network client. Impact is at least local denial of service and may include host memory disclosure to a guest or local tenant. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES SIMPLEFIX LINUS KPANIC MEMORY KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 5
* Conservative score: 5
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 Strong read based primitive. A negative ssize_t result from vringh_iov_pull_iotlb() is converted to a very large size_t length and is passed to receive_filter() and vringh_iov_push_iotlb(). The supplied patch directly establishes a potentially unbounded out of bounds read from the PAGE_SIZE net buffer.
* +1 Confidentiality plausible. The oversized length reaches vringh_iov_push_iotlb(), which is an RX copy path into a virtqueue buffer controlled by the vDPA consumer. This provides a plausible host memory to guest output path, not merely an internal invalid read.
* +1 Cross boundary isolation concern. The affected path is a simulated virtio network device. If an assigned guest can supply malformed virtqueue descriptors, host kernel memory beyond net->buffer may be copied into guest visible RX memory.
* +1 Reliable kernel crash or strong DoS. A very large source length can cause invalid host kernel memory accesses during filtering or RX copying.
Important non awarded signals:
* No arbitrary or directed host kernel write is demonstrated.
* No UAF, refcount misuse, controlled reclaim, callback control, or type confusion is demonstrated.
* No privilege escalation is demonstrated.
* No direct external network reachability is established. The malformed input is delivered through a vDPA virtqueue, not directly through a network listener.
* No separate local unprivileged high control API point is awarded because the supplied evidence does not establish that an ordinary host user can create, configure, and operate the complete vDPA simulator path without delegated access or prior host provisioning.
* No additional Availability point is awarded because the potential crash is already counted once.
* No additional paranoid point is awarded. The host memory disclosure and crash mechanisms are already reflected in the conservative score.
3. Reachability analysis
The likely attacker is a malicious guest or another below host admin actor that controls descriptors for an already assigned vDPA simulated network device. Such an actor can cause vringh_iov_pull_iotlb() to fail and can then drive the TX to RX processing path.
The vDPA simulator device normally requires prior host side provisioning, attachment, or exposure to a guest. That provisioning is a deployment prerequisite, but the attacker does not necessarily need host administrator privileges after the device is assigned. Therefore HostAdminRequired is NO for the trigger model involving an untrusted guest with an assigned device.
Namespace scoped privilege is UNKNOWN. The supplied patch does not show the device creation, vDPA management, IOMMU setup, guest assignment, or capability checks. It is not established that the full vulnerable sequence can be created solely with attacker controlled namespace capabilities.
No rare physical hardware requirement is indicated. This is a software vDPA simulation path. No race or narrow timing condition is required. The malformed descriptor and pull failure can likely be retried repeatedly by the entity controlling the virtqueue.
4. Primitive and severity interpretation
The bug is a signed to unsigned length conversion vulnerability. A failed TX pull returns a negative signed byte count. Before the fix, that value could be passed as a size_t length into receive_filter() and vringh_iov_push_iotlb(). The negative value can therefore become a very large positive length while net->buffer remains only PAGE_SIZE bytes.
This is not a UAF and does not involve stale lifetime state. It is an out of bounds host memory read with a plausible output sink because the oversized length reaches the RX virtqueue copy path. The relevant storage is a fixed host network buffer, but the resulting copy may expose bytes beyond that buffer to the guest or vDPA consumer.
The demonstrated practical consequences are host kernel crash or DoS and potential host memory disclosure across a guest to host isolation boundary. Integrity impact is not established because the patch does not show a host memory write beyond an intended destination, active object replacement, or attacker directed overwrite.
PrimitiveClass is CLASS_A because the patch supports a meaningful host memory disclosure primitive through a device output path. ImportantCandidate is YES because the actual amount, contents, and practical reachability of copied host memory require validation in the full vringh_iov_push_iotlb() path. AutoDowngradeAllowed is NO because automatically treating this as a normal crash bug could miss a guest visible host memory disclosure condition.
5. One-sentence report phrase
A negative vringh_iov_pull_iotlb result could be converted into a large size_t length and used for RX processing, potentially causing a host kernel crash and copying memory beyond the vDPA simulated network buffer into a guest controlled virtqueue.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Verify the complete vringh_iov_push_iotlb() source and destination bounds behavior, determine whether guest controlled RX buffers can receive bytes beyond net->buffer, and confirm which users or guests can operate an assigned vdpa_sim_net device.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: vdpa_sim_net: check TX pull result before RX copy [ Upstream
Commit: c001abcde865b74231da8f1412c3217dbf66781e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c001abcde865b74231da8f1412c3217dbf66781e
Changed files:
drivers/vdpa/vdpa_sim/vdpa_sim_net.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=c001abcde865b74231da8f1412c3217dbf66781e
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97990 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97990
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:L/UI:N/S:U/C:L/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
The Best / paranoid CVSS score: 7.1
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: 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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