[CVE-2026-98603][MODERATE 7.0] ovpn: replace bind when clearing stale local source [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-98603
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ovpn: replace bind when clearing stale local source [ Upstream
Commit: c44a04722f7dae9a45a101b8e100931ab59f1c18
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c44a04722f7dae9a45a101b8e100931ab59f1c18
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98603
Analysis date: Mon, 19 Oct 2026 05:09:13 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
An in-place update of an RCU-published OVPN bind can expose a torn IPv6 source address to concurrent TX and route-cache consumers, creating an actionable routing-integrity and availability issue whose delegated-interface boundary requires manual review.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98603 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98603

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98603	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98603 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-362;CWE-667;CWE-662;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.8';DESCR 'An RCU published ovpn bind can be modified in place while concurrent TX paths read it without locking. When a remembered IPv6 source address becomes unusable, clearing the 128 bit local address can be observed as a torn value and may cause route lookup or cached routing state to use an inconsistent source address. The most credible effects are packet loss, incorrect source address selection, disruption of an OVPN peer, or limited interaction with source based routing policy. No UAF, OOB access, arbitrary write, or direct kernel crash primitive is established by the shown code. For the CVSS the PR:L value in the paranoid score represents deployments where a container or restricted network service has delegated control over its OVPN interface or network namespace. The race requires the remembered local source to become invalid while concurrent transmission is active, so AC:H is appropriate. A remote peer can contribute traffic but cannot reliably trigger the required local address invalidation through network traffic alone. Impact is primarily availability related, with limited confidentiality or integrity impact remaining possible if an inconsistent source selects an unintended routing path. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.8 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 MODERATE_KPANIC because KP specialist did not establish a qualifying panic. 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_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP. The independent weaker Aegis shadow evaluated CVSS 1.9 and ActionableScore 1 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	OOB LOCK NETWORK HARDWARE LINUS IPV6 KPANIC PACKET  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 5
* Raw paranoid score: 4
* Paranoid score: 5
* Applied conservative floor: 3 -> 5 due to the V33 active-state and unresolved trust-boundary review rule.
* Applied paranoid floor: 4 -> 5 for the same mandatory review condition.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +1 Weak or indirect structured-state corruption. The writer clears the 128-bit `bind->local.ipv6` field in an RCU-published object while lockless TX readers may copy it.
* +1 Realistic availability impact. A torn source address can cause failed route lookup, packet loss, stale destination-cache use, or disruption of the OVPN peer.
* +1 Networking packet-processing and routing consumption. The inconsistent source is consumed by `ip6_dst_lookup_flow()` and can influence common IP routing and destination-cache state.
* Raw conservative total: 3.

Paranoid additional signal:

* +1 Limited integrity concern. The torn source address can alter packet identity, source-based route selection, or policy selection before transmission. This is not an arbitrary write or a proven policy bypass.
* Raw paranoid total: 4.

Important non-awarded signals:

* No UAF, post-lifetime access, OOB access, refcount corruption, or repeated release is established.
* No arbitrary or attacker-directed kernel-memory write is established.
* No reliable kernel crash, information disclosure, privilege escalation, or remote-only trigger is demonstrated.
* No separate availability point was awarded for a kernel panic because no panic is supported.
* No authorization signal applies. The patch does not change a DENY decision into ALLOW.
* No local-unprivileged bonus or privilege penalty was applied because the complete capability and namespace boundary is unresolved.

V33 decomposition:

1. Write: the fallback writes a wildcard value into the active, RCU-published local IPv6 address in place.
2. Privileged consumer: the kernel TX path copies that state into `flowi6`, performs route lookup, and may update per-CPU destination-cache state.
3. Boundary: a namespace-controlled or delegated OVPN interface is credible, but the supplied evidence does not prove that all configuration, address invalidation, and TX stages are available below host-admin privilege.
4. Consequence: inconsistent packet source and routing state are demonstrated risks. Host panic, cross-namespace policy bypass, and host compromise remain unproven.

3. Reachability analysis

The required sequence is an OVPN UDP peer with a remembered local source address, invalidation of that address, and concurrent TX while the fallback clears the published bind. A remote peer may contribute traffic but cannot, from the supplied evidence, independently invalidate the local address.

An actor controlling the OVPN interface and local address configuration can plausibly influence both state invalidation and TX load. The exact requirement for host `CAP_NET_ADMIN`, namespace-scoped `CAP_NET_ADMIN`, a delegated interface, or prior host setup is not resolved. Therefore `HostAdminRequired` and `NamespaceScopedPrivilege` remain `UNKNOWN`.

The bug is a race, but no timing penalty is applied. The commit does not establish that the window is one-shot, exceptionally narrow, or impractical under concurrent TX load.

4. Primitive and severity interpretation

The primitive is a torn read of an actively used 128-bit IPv6 address caused by modifying an RCU-published structured object in place. This is active structured-state corruption, not a lifetime violation or heap-memory corruption.

The stale or inconsistent value is used beyond cleanup. It participates in source-address selection, route lookup, transmission, and destination-cache handling. The demonstrated consequence is incorrect routing state and VPN traffic disruption. A limited routing or packet-identity integrity effect is technically defensible, but cross-boundary policy bypass and host-wide failure are unresolved.

`PrimitiveClass=CLASS_B` reflects a concrete active-state synchronization defect with a meaningful downstream consumer. `ImportantCandidate=YES` preserves the unresolved delegated-interface or namespace trust-boundary question for review. It does not assert Important severity, arbitrary kernel access, or privilege escalation.

`AutoDowngradeAllowed=NO` follows from the V33 candidate chain. Automatic closure would discard the unresolved question of whether attacker-controlled interface state can affect a more privileged routing context.

5. One-sentence report phrase

An in-place update of an RCU-published OVPN bind can expose a torn IPv6 source address to concurrent TX and route-cache consumers, creating an actionable routing-integrity and availability issue whose delegated-interface boundary requires manual review.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Confirm which namespace governs OVPN peer configuration and address removal, whether a delegated actor can drive the complete race, and whether the malformed source can cross into host routing, netfilter, or policy-routing contexts.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ovpn: replace bind when clearing stale local source [ Upstream
Commit: c44a04722f7dae9a45a101b8e100931ab59f1c18
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c44a04722f7dae9a45a101b8e100931ab59f1c18

Changed files:
  drivers/net/ovpn/udp.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=c44a04722f7dae9a45a101b8e100931ab59f1c18

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

The original Linux kernel CVE announcement for CVE-2026-98603 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98603

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:H/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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