* [CVE-2026-98098][MODERATE REGULAR] tipc: fix NULL deref in tipc_named_node_up() on empty publication list [ Upstream
@ 2026-09-25 19:16 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 19:16 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98098
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: tipc: fix NULL deref in tipc_named_node_up() on empty publication list [ Upstream
Commit: 68619f965329d2f7b113a3d5811aa23198f39105
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68619f965329d2f7b113a3d5811aa23198f39105
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98098
Analysis date: Fri, 25 Sep 2026 15:16:30 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
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-2026-98098 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98098
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-2026-98098 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98098 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:N/I:N/A:H';**CWE-476;**CWE-400;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference can occur in tipc_named_node_up because local applications can fill the TIPC name table with user publications and prevent the internal node state service from being registered. A later node event can leave the publication output list empty, causing skb_peek_tail to return NULL before buf_msg dereferences it in the receive path. For the CVSS the PR:L value is used because reliable triggering requires a local user or process that can create TIPC sockets and register a large number of service addresses. Network activity may supply the later node event, but network access alone is not sufficient without the local publication exhaustion step. Impact is denial of service through a kernel NULL pointer dereference and crash. The available code shows no UAF, OOB write, information disclosure, or controlled memory corruption primitive, so confidentiality and integrity remain unaffected.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE OOB DANGER NULLPTR TIPC SKB HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=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
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +1 Local unprivileged trigger. The supplied evidence states that user-space applications can bind enough local-scope TIPC service addresses to exhaust the publication limit. The supplied PR:L assessment also supports below-host-admin reachability.
* +1 Reliable kernel crash / strong DoS. An empty publication list causes `skb_peek_tail()` to return NULL, which is passed to `buf_msg()` and dereferenced in `tipc_named_node_up()`.
* +1 Distinct availability effect. Publication exhaustion also prevents registration of internal node and link service types, causing subscribers to stop receiving topology notifications independently of the eventual kernel crash.
* No remote-reachability bonus. Network activity can provide the later node event, but remote traffic alone cannot create the required publication-exhaustion state.
* No UAF or memory-corruption bonus. The established primitive is a NULL dereference caused by invalid empty-list handling.
* No resource-leak bonus. The table is deliberately filled with bounded publications. No lost reference or missing release is shown.
* No race penalty. The shown two-thread sequence explains how the invalid state is observed, but the failure does not depend on a demonstrated narrow or unreliable timing window once the table is saturated.
* No extra availability point for crash repeatability. The crash is counted once.
* No confidentiality, integrity, LPE, controlled reclaim, arbitrary write, OOB access, or structured stale-object leverage is established.
3. Reachability analysis
An ordinary local process with access to TIPC sockets can create many local-scope service bindings until `local_publ_count` reaches the limit. The supplied evidence does not identify a host-admin capability check for these binding operations, so below-host-admin reachability is positively supported and `HostAdminRequired=NO`.
A later TIPC node event reaches `tipc_named_node_up()` through the receive path and exposes the empty publication list. This event may originate from network activity, but the complete attack is not remotely triggerable because the attacker must first prepare the local name-table state.
The vulnerable environment must have TIPC enabled and operational, potentially including prior administrative bearer or network configuration. This prerequisite does not show that the attacking process itself requires host-admin privilege. The supplied material does not establish whether the complete sequence can be created entirely inside an attacker-controlled user and network namespace, so `NamespaceScopedPrivilege=UNKNOWN`.
The publication exhaustion is repeatable and does not require special hardware. No hard-race penalty is justified.
4. Primitive and severity interpretation
The exact primitive is an invalid NULL-pointer dereference. Publication exhaustion prevents an internal protocol publication from being inserted. The distribution path subsequently obtains NULL from `skb_peek_tail()` on an empty queue and dereferences it through `buf_msg()`.
This is neither fixed stale storage nor an active structured-object UAF. No object is shown to be used after free, and no repeated release or refcount mutation exists. The demonstrated consequence is a kernel crash plus loss of topology notifications. Theoretical escalation beyond DoS is unsupported because there is no attacker-directed write, stale-object reuse, disclosure path, or lifetime-corruption primitive.
`PrimitiveClass=CLASS_C` is therefore appropriate. `ImportantCandidate=NO` because the evidence establishes crash and service disruption only. `AutoDowngradeAllowed=YES` because no unresolved corruption, ownership, lifetime, or authorization primitive would be discarded by treating this as an ordinary Moderate-class DoS. Operational severity is Moderate and configuration-dependent.
5. One-sentence report phrase
A local low-privilege TIPC user can exhaust the publication table so that a later node event dereferences an empty publication list and crashes the kernel, but no memory-corruption or privilege-escalation primitive is established.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm the exact TIPC socket privilege and namespace requirements for the affected product, but the supplied code supports only a local NULL-dereference DoS and does not justify Important-class treatment.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: tipc: fix NULL deref in tipc_named_node_up() on empty publication list [ Upstream
Commit: 68619f965329d2f7b113a3d5811aa23198f39105
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68619f965329d2f7b113a3d5811aa23198f39105
Changed files:
include/linux/skbuff.h
net/tipc/name_distr.c
net/tipc/node.c
net/tipc/udp_media.c
net/tipc/name_table.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=68619f965329d2f7b113a3d5811aa23198f39105
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98098 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98098
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: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: 3
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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