* [CVE-2026-99279][MODERATE 7.0] ksmbd: reclaim ended sessions on logoff and expiration
@ 2026-11-08 2:18 21% AL-KERNEL
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From: AL-KERNEL @ 2026-11-08 2:18 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99279
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ksmbd: reclaim ended sessions on logoff and expiration
Commit: 1767a5e45dbf6a3b12105196dda4fb0ef80b9698
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1767a5e45dbf6a3b12105196dda4fb0ef80b9698
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99279
Analysis date: Sat, 07 Nov 2026 22:18:29 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
Authenticated remote SMB clients can repeatedly leave ended ksmbd sessions and associated resources retained, potentially degrading service through accumulated resource consumption.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99279 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99279
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-2026-99279 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99279 CHECK WITH IMPACT FROM ORIG NN NONE | AEGIS IMPACT MODERATE AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE_KPANIC, Aegis: MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;**CWE-400;Other CVSS 'AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.5';DESCR 'Ended ksmbd sessions can remain published after LOGOFF, previous session replacement, or expiration and can retain allocated memory, connection references, procfs state, and limited session slots when no later setup request reaches the owning connection. A remote SMB client with a valid session can repeat session creation and termination to accumulate retained resources and degrade service availability. For the CVSS the PR:L value is selected because the reliable LOGOFF trigger requires an established SMB session, while unauthenticated SessionId zero cleanup does not by itself establish reliable host wide exhaustion. The demonstrated primitive is persistent resource retention rather than memory corruption. Base availability impact is low because immediate host failure is not shown, while sustained abuse could potentially exhaust ksmbd resources and justify high availability impact in the paranoid case. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 6.5 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the ActionableScore threshold rule was applied. 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_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4. The independent weaker Aegis shadow evaluated CVSS 4.3 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE REMOTE DISK INIT LEAK SKIP LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base 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
* +2 remote reachability: an authenticated SMB client can invoke session LOGOFF and repeat session creation/termination over the network.
* +1 concrete persistent resource/reference leak: ended sessions remain globally published and retain memory, connection references, procfs state, and session slots until an owning-connection setup happens.
* Paranoid +1 availability: repeated retained sessions can plausibly exhaust limited ksmbd session/connection resources and degrade service. This is not included in the conservative score because host-wide exhaustion or failure is not demonstrated.
* No memory corruption, UAF, OOB access, repeated release, authorization bypass, confidentiality impact, or integrity impact is shown.
* No reliable kernel crash point: the patch addresses delayed reclamation and bounded slots rather than a panic path.
* NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of corrupted structured state.
* NEW53/B3-PENDING and NEW54/B4-PENDING do not apply.
3. Reachability analysis
A remote client with a valid SMB session can issue LOGOFF and repeat the lifecycle sequence; this is below host-administrator privilege and does not require host UID 0. Authentication is a service-level prerequisite, not host administration. No special hardware, namespace capability, race, or boot option is shown. Namespace scoping is unresolved and immaterial to the demonstrated network-service resource leak.
4. Primitive and severity reading
The primitive is persistent retention of ended session objects and associated references/slots, classified CLASS_C because the supported consequence is resource depletion/availability degradation rather than memory corruption or unsafe post-lifetime use. The fix unpublishes sessions, removes procfs entries, drops table references, and adds expiration-worker reclamation. Strong host-wide exhaustion is plausible but unproven. ImportantCandidate is therefore NO, and automatic downgrade remains allowed.
5. One-sentence report phrase
Authenticated remote SMB clients can repeatedly leave ended ksmbd sessions and associated resources retained, potentially degrading service through accumulated resource consumption.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm practical accumulation limits and whether sustained authenticated abuse can exhaust host-wide memory or only ksmbd-local session capacity.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ksmbd: reclaim ended sessions on logoff and expiration
Commit: 1767a5e45dbf6a3b12105196dda4fb0ef80b9698
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1767a5e45dbf6a3b12105196dda4fb0ef80b9698
Commit description:
LOGOFF and previous-session replacement leave sessions Expired with a
zero credential expiry. Ended sessions can retain their memory and
connection slots when no further setup arrives on the owning connection.
Unpublish a logged-off session while the request reference keeps its
response signing and encryption keys alive. Remove its procfs entry
before dropping the table reference so a reader cannot remove its own
entry on the last put. Clear proc_entry after removal to avoid removing
it twice.
Reclaim ended sessions from the global table in the existing expiration
worker before it acquires conn_list_lock. Only select Expired sessions
with zero credential expiry and no references beyond the table
reference. Keep sessions whose Kerberos credentials expired available
for reauthentication.
Unlink the session from its setup connection and all channel
connections, so SMB2 sessions and sessions with only secondary SMB3
channels are covered. The session already holds connection references,
and sessions_table_lock prevents concurrent channel removal. Queue
sessions on a separate disposal list, leaving their hash nodes unhashed,
and remove procfs entries and drop table references outside the locks.
Keep the pending setup check before allocating a new session so
abandoned InProgress sessions can release their slots even at the
connection limit. Retain the timeout and reference checks and dispose of
those sessions outside the locks. Leave ended Expired sessions to the
expiration worker.
Fixes: d7fd1f9 ("ksmbd: follow SMB2 session expiration semantics")
Cc: [email protected]
Reported-by: Abdifatah Suruur <[email protected]>
Signed-off-by: Namjae Jeon <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
fs/smb/server/connection.c
fs/smb/server/mgmt/user_session.c
fs/smb/server/mgmt/user_session.h
fs/smb/server/smb2pdu.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=1767a5e45dbf6a3b12105196dda4fb0ef80b9698
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99279 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99279
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:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 6.5
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: 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: 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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