[CVE-2026-98493][IMPORTANT] net: ipconfig: bound DHCP option construction [ Upstream

[CVE-2026-98493][IMPORTANT] net: ipconfig: bound DHCP option construction [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98493
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: net: ipconfig: bound DHCP option construction [ Upstream
Commit: abcba6f080c63e403037ecdffde43170d242376a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=abcba6f080c63e403037ecdffde43170d242376a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98493
Analysis date: Sat, 24 Oct 2026 11:25:31 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Oversized locally configured DHCP hostname and vendor-class options can overwrite approximately 26 bytes beyond `bootp_pkt.exten[]`, causing a fortified boot panic and unresolved adjacent kernel-state corruption.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-98493 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98493

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: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98493	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-98493 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-787;CWE-120;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'ic_dhcp_init_options can exceed the fixed 312 byte bootp_pkt exten field when a maximum length hostname and dhcpclass value are combined. The vendor class memcpy can write about 26 bytes beyond exten and the END marker can extend the overwrite by one more byte. CONFIG_FORTIFY_SOURCE reports the field spanning write and panic_on_warn can turn it into a deterministic boot time denial of service. Lacking that configuration this remains a bounded memory corruption issue, but no specific sensitive target, arbitrary write, information leak, or reliable privilege escalation path is established. The issue is not remotely triggered by a DHCP response because the relevant values come from local boot or provisioning configuration. For the CVSS the PR:L value in the paranoid vector reflects environments where a VM tenant or delegated provisioning user can select these boot parameters without full host administration rights. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 6.6 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. KP and FD specialist checks stage IMPORTANT to IMPORTANT because a specific evidence based protection or manual review veto 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 produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and V42_LEGACY_CLASSA_FD_VETO and MANUAL_REVIEW_REQUIRED and TEMP_KPANIC_MERGE_IMPORTANT_WINS. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 0 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	REMOTE DANGER INIT NETWORK KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS V42_LEGACY_CLASSA_FD_VETO MANUAL_REVIEW_REQUIRED TEMP_KPANIC_MERGE_IMPORTANT_WINS	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 3.
* Conservative score: 5. Manual-review safety floor raises 3 -> 5 for a confirmed, payload-influenced kernel-buffer OOB write.
* Raw paranoid score: 3.
* Paranoid score: 5. No additional speculative effects awarded.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong corruption primitive: hostname and vendor-class lengths can make `memcpy()` write roughly 26 bytes beyond the fixed 312-byte `exten[]`; vendor-class bytes materially influence the overflow payload.
* +1 Reliable kernel crash/strong DoS: FORTIFY detects the field-spanning write, and `panic_on_warn=1` aborts boot.
* No privilege penalty: effective privileges needed to select the complete boot/provisioning configuration are unresolved.
* No extra availability point: the boot panic is the same crash already counted.
* No confidentiality, protected-state integrity, arbitrary-target write, controlled reclaim, adjacent victim, or LPE is shown.
* B5-R does not apply: no retry/re-entry accumulation or later consumption of retry-corrupted structured state is present.
* B4-PENDING does not apply: there is no authorization decision or DENY-to-ALLOW transition.

3. Reachability analysis

The inputs originate from local boot or provisioning configuration, not DHCP response traffic. The supplied hints describe possible VM-tenant or delegated-provisioning control, but the patch does not establish a complete below-host-admin interface or its credentials. Consequently, host-admin requirement and host UID 0 requirement remain unknown. Kernel boot configuration is not namespace-scoped, and no race, retry loop, special hardware, or remote trigger is involved.

4. Primitive and severity reading

The exact primitive is a bounded, attacker-data-influenced OOB write past a fixed DHCP packet option field. It is not a UAF and no later corrupted pointer or descriptor consumer is shown. The demonstrated consequence is a configuration-dependent boot panic; non-crash exploitation remains unresolved. CLASS_A is appropriate for the confirmed controlled-byte OOB write, but stronger impact claims are unsupported. ImportantCandidate is YES and automatic downgrade is disallowed because a real kernel-buffer overwrite would otherwise be discarded without examining the enclosing allocation and adjacent state.

5. One-sentence report phrase

Oversized locally configured DHCP hostname and vendor-class options can overwrite approximately 26 bytes beyond `bootp_pkt.exten[]`, causing a fortified boot panic and unresolved adjacent kernel-state corruption.

6. Manual review advice

MANUAL CHECK REQUIRED

Review the enclosing packet allocation, overwritten adjacent storage, and whether delegated provisioning or VM boot-parameter control supplies a below-host-admin trigger.

7. Call-site confidence

Call-site confidence: medium

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: net: ipconfig: bound DHCP option construction [ Upstream
Commit: abcba6f080c63e403037ecdffde43170d242376a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=abcba6f080c63e403037ecdffde43170d242376a

Changed files:
  net/ipv4/ipconfig.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=abcba6f080c63e403037ecdffde43170d242376a

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DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-98493 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98493

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:H/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:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).