* [CVE-2026-98402][LOW] net: icmp: avoid invalid transport header access in icmp_send tracepoint [ Upstream
@ 2026-10-15 9:38 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-15 9:38 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98402
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: icmp: avoid invalid transport header access in icmp_send tracepoint [ Upstream
Commit: ec6d4612d1c170e1cef1fe55526471da1e81e777
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ec6d4612d1c170e1cef1fe55526471da1e81e777
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98402
Analysis date: Thu, 15 Oct 2026 05:38:55 -0400
ActionableScore: 0
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-2026-98402 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98402
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-2026-98402 LOW https://www.kernelcve.org/list/?q=CVE-2026-98402 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-20;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'The icmp_send tracepoint accessed UDP transport metadata before confirming that the packet was UDP and before establishing that skb transport_header had been initialized. Network error paths such as link failure, ARP error, forwarding, and AF_PACKET processing can reach __icmp_send with transport_header left unset, causing DEBUG_NET_WARN_ON_ONCE when CONFIG_DEBUG_NET is enabled and the tracepoint is active. For the CVSS the PR:L reflects that the demonstrated and reliably controlled trigger requires a local process able to exercise the relevant networking path, while a reliable unauthenticated remote trigger is not established by the available code. AC:H reflects the required combination of tracepoint activation, a suitable ICMP generation path, and an skb without initialized transport metadata. The demonstrated impact is a warning and limited availability degradation. The paranoid impact is denial of service if the system converts the warning into a panic through panic_on_warn. There is no supported UAF, out of bounds write, information leak, or privilege escalation primitive, so confidentiality and integrity remain unaffected. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE WARNONLY TRACE SKB LINUS SYZBOT PACKET - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +0 WARN-only behavior. The demonstrated result is DEBUG_NET_WARN_ON_ONCE under CONFIG_DEBUG_NET, not a kernel crash, memory overwrite, disclosure, or persistent failure.
* +0 Invalid metadata access. udp_hdr() invokes skb_transport_header() with an unset transport-header offset, but the evidence does not establish an actual out-of-bounds read or write.
* +0 Networking exposure. The code is in an ICMP packet-processing path, but execution of TP_fast_assign requires the icmp_send tracepoint to be active. Direct unauthenticated remote reachability is not established.
* +0 Availability. WARN_ON alone does not qualify as reliable kernel DoS. A panic_on_warn configuration would make the warning fatal, but no such deployed configuration or observed panic is supplied.
* No race, privilege, hardware, rarity, or configuration penalty was applied.
* Controlled corruption, arbitrary write, controlled reclaim, UAF, disclosure, privilege escalation, and authorization bypass are not demonstrated.
* NEW52 B5-R does not apply. There is no confirmed heap OOB write, retry-accumulated index, or later consumption of corrupted structured state.
* NEW53 B3-PENDING does not apply. No shared or file-backed storage is modified.
* NEW54 B4-PENDING does not apply. No mandatory authorization decision changes from DENY to ALLOW.
3. Reachability analysis
The observed call path reaches the tracepoint through ICMP generation after a VTI link failure, and the commit also identifies ARP errors, forwarding, and AF_PACKET paths. A local process may be able to exercise some of these paths, but the supplied evidence does not establish the permissions required for the complete reproducer.
The vulnerable tracepoint assignment executes only when the icmp_send tracepoint is enabled. Enabling kernel tracing commonly requires privileged setup, but the exact tracefs policy, prior setup, and attacker role are not supplied. Therefore HostAdminRequired remains UNKNOWN rather than being inferred as either YES or NO.
The presence of networking paths does not establish that the complete trigger is namespace-scoped. No capability check or complete user-namespace and network-namespace trigger chain is shown, so NamespaceScopedPrivilege is UNKNOWN. No special hardware is required by the underlying tracepoint defect, although the reported stack used VTI. There is no race or retry requirement.
4. Primitive and severity interpretation
The exact defect is an invalid transport-header metadata access in a tracepoint. TP_fast_assign calls udp_hdr() before verifying that the packet is UDP and while skb->transport_header may still contain its unset sentinel value. Under CONFIG_DEBUG_NET, skb_transport_header() detects this and emits a warning.
This is CLASS_C because the demonstrated behavior is invalid-state access and a diagnostic warning. It is not a real UAF, lifetime violation, OOB write, shared-backing write, or authorization bypass. The patch does not establish that an invalid UDP header is dereferenced before the existing protocol and bounds checks reject it.
The practical consequence is a warning and possible diagnostic disruption. A kernel panic is only a configuration-dependent theoretical consequence if warnings are configured as fatal. There is no independently useful primitive remaining after excluding that warning.
ImportantCandidate is NO because no corruption, ownership, lifetime, authorization, or security-boundary primitive is established. AutoDowngradeAllowed is YES because this is a constrained warning-only defect with no unresolved exploitation leverage.
5. One-sentence report phrase
The icmp_send tracepoint could inspect an unset SKB transport-header offset and trigger a DEBUG_NET warning, but the supplied evidence establishes neither memory corruption nor a reliable security-boundary impact.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch addresses a diagnostic invalid-state access with no demonstrated UAF, OOB write, disclosure, authorization bypass, or reliable crash primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: icmp: avoid invalid transport header access in icmp_send tracepoint [ Upstream
Commit: ec6d4612d1c170e1cef1fe55526471da1e81e777
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ec6d4612d1c170e1cef1fe55526471da1e81e777
Changed files:
include/linux/skbuff.h
include/linux/udp.h
include/trace/events/icmp.h
net/ipv4/icmp.c
net/ipv4/route.c
include/net/dst.h
net/ipv4/ip_vti.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=ec6d4612d1c170e1cef1fe55526471da1e81e777
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98402 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98402
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:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.7
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: 0
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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