* [CVE-2026-90107][MODERATE REGULAR] net/smc: free pending qentry in smc_llc_flow_stop() before memset [ Upstream
@ 2026-09-18 1:42 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 1:42 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90107
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net/smc: free pending qentry in smc_llc_flow_stop() before memset [ Upstream
Commit: 8e3deb150a5237b672c4579e69a6deb02027dbed
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8e3deb150a5237b672c4579e69a6deb02027dbed
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90107
Analysis date: Thu, 17 Sep 2026 21:42:35 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90107 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90107
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 REGULAR
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-2026-90107 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90107 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'An SMC LLC flow can leak a pending qentry because smc_llc_flow_stop() clears the whole flow structure with memset while flow qentry may still point to an allocated object. A late duplicate CONFIRM_LINK or ADD_LINK_CONT message can place a new qentry into the flow after the normal waiter consumed the legitimate message but before the flow is stopped. For the CVSS the PR:N is used for the paranoid score because a remote SMC peer does not need privileges on the victim host once it can participate in the SMC link context. The attack is best treated as adjacent network rather than public Internet exposure because SMC is normally used between configured peers in data center or RDMA capable environments. Impact is denial of service through accumulated kernel memory leaks. No direct confidentiality impact, integrity impact, UAF, OOB access, or privilege escalation primitive is indicated by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) YES LEAK IMPROVEONLY LINUS INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3. No floor or cap applied.
* Raw paranoid score: 4
* Paranoid score: 4. No floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
Conservative positive signals:
* +2 Remote or network-adjacent protocol reachability: attacker-controlled SMC LLC duplicate messages can reach the vulnerable logic once an SMC link context exists.
* +1 Concrete persistent kernel resource/reference leak: flow->qentry can be overwritten by memset without freeing the allocated qentry object.
Paranoid additional signal:
* +1 Sustained resource exhaustion concern: repeated successful hits of the duplicate-message timing window could accumulate leaked kmalloc objects and cause memory-pressure DoS.
Negative signals:
* No -1 race penalty applied. The bug involves a timing window, but the duplicate-message condition appears retryable by a peer and is not proven to be one-shot or externally uncontrollable.
* No -1 niche-subsystem penalty applied. SMC is specialized, but specialization alone is not sufficient evidence for a reducing signal.
Important non-awarded signals:
* RealUAF not awarded. The pointer is lost before free, but no stale post-lifetime use is established.
* Concrete repeated release/refcount not awarded. There is no first put/free followed by a second lifetime mutation on the same dangling reference.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity not awarded. The established primitive is a memory leak, not disclosure or unauthorized modification.
* Strong LPE and weak LPE not awarded. No exploitation primitive beyond resource leakage is supported.
* Extra availability not double-counted. The paranoid availability concern is sustained accumulation, not the same single leak event.
3. Reachability analysis
The likely attacker is a remote or adjacent SMC peer able to send late duplicate CONFIRM_LINK or ADD_LINK_CONT LLC messages during an active SMC link flow. No privilege on the victim host is required once the vulnerable SMC communication path is reachable, so HostAdminRequired is NO.
The complete path likely requires SMC to be enabled and in use, and requires an SMC link group or peer relationship to exist. This is a deployment prerequisite, not evidence that the attacker needs host-admin-equivalent privilege on the victim. SMC is typically used in controlled data-center or RDMA-capable environments rather than exposed to the public Internet.
NamespaceScopedPrivilege is UNKNOWN because the supplied evidence does not establish that the complete SMC trigger chain is namespace-scoped. The timing condition is a late duplicate arriving after the legitimate message is consumed and before smc_llc_flow_stop clears the flow. It is a real window, but repeated protocol attempts may be possible.
4. Primitive and severity interpretation
The exact primitive is a concrete kernel memory leak: smc_llc_flow_stop clears the flow structure with memset while flow->qentry may still reference an allocated qentry. The allocation is then no longer reachable by normal cleanup.
This is not a UAF, not a double free, and not a repeated refcount/lifetime mutation. The affected flow object is structured kernel state, but the stale effect is only loss of a pointer before release. There is no evidence that freed memory is reused, that stale fields are consumed after free, or that attacker-controlled contents influence callbacks, credentials, object selection, or kernel writes.
PrimitiveClass is CLASS_C because the demonstrated behavior is resource-leak DoS without an independently useful corruption primitive. ImportantCandidate is NO because the patch supports resource exhaustion only, not memory corruption, ownership violation, authorization bypass, or privilege escalation. AutoDowngradeAllowed is YES because no unresolved Important-grade primitive remains, although manual review is still recommended due to protocol-driven network-adjacent reachability.
Operational severity is low to borderline moderate. The main practical risk is accumulated kernel memory leakage under repeated duplicate-message triggering.
5. One-sentence report phrase
An SMC LLC flow can leak a pending qentry when a late duplicate CONFIRM_LINK or ADD_LINK_CONT message is stored before smc_llc_flow_stop clears the flow, allowing a network-adjacent SMC peer to cause accumulated kernel memory leakage and potential DoS.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Reason: the issue appears to be resource-leak DoS only, but it is protocol-driven and potentially reachable from an SMC peer, so exposure and repeatability should be checked before automatic closure.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net/smc: free pending qentry in smc_llc_flow_stop() before memset [ Upstream
Commit: 8e3deb150a5237b672c4579e69a6deb02027dbed
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8e3deb150a5237b672c4579e69a6deb02027dbed
Changed files:
net/smc/smc_llc.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=8e3deb150a5237b672c4579e69a6deb02027dbed
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90107 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90107
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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.3
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: 3
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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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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