* [CVE-2026-98569][MODERATE REGULAR] ip_gre: Reject enabling collect metadata through changelink [ Upstream
@ 2026-10-19 2:46 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-19 2:46 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98569
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ip_gre: Reject enabling collect metadata through changelink [ Upstream
Commit: c80315da84998b69b8829785a174b0bf72a81992
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c80315da84998b69b8829785a174b0bf72a81992
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98569
Analysis date: Sun, 18 Oct 2026 22:46:53 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A namespace administrator could use the GRE changelink path to violate metadata tunnel uniqueness, replace a shared receive registration, and later disrupt metadata packet lookup for another tunnel in the same network namespace.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98569 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98569
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: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98569 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98569 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME V39_AEGIS_ONE_STEP_UP=LOW->MODERATE (final reconciliation agrees; DECISION: both 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:L/I:L/A:L';CWE-670;*CWE-664;CWE-706;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'The ip_gre changelink path could enable collect_md on an existing GRE, GRETAP, or ERSPAN device without enforcing the metadata tunnel uniqueness rule used by newlink. This could replace the shared metadata receive entry for another device in the same network namespace. Deleting either device could then clear the shared entry and break metadata receive lookup for the surviving device. A validation failure after collect_md was set could produce a similar ownership mismatch. For the CVSS the PR:L value is used in the paranoid score because container root, a service account, or another restricted actor may be delegated CAP_NET_ADMIN in the affected network namespace without having full host privileges. The issue is not directly reachable through ordinary network packets because triggering requires a local netlink control plane operation. The demonstrated impact is limited disruption of GRE metadata receive. Limited confidentiality or integrity impact is retained only as a conservative possibility if traffic is temporarily associated with the wrong metadata device in the same network namespace. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. 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. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE REMOTE SIMPLEFIX NETWORK HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=YES
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 1.
* Conservative score: 1.
* Raw paranoid score: 1.
* Paranoid score: 1.
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Weak or indirect active-state corruption candidate. `changelink` can replace the shared metadata receive registration with another device and create an ownership mismatch.
* +1 Availability impact. Deleting either implicated device can clear the shared registration and break metadata receive lookup for the surviving device.
* -1 Reduced namespace-scoped privilege. The operation passes `rtnl_dev_link_net_capable()` and therefore requires `CAP_NET_ADMIN` relative to the target network namespace, but not necessarily host-administrator authority.
* No UAF, OOB access, arbitrary write, kernel crash, disclosure, authorization bypass, or privilege escalation is established.
* No integrity point was awarded. The wrong receive registration is an internal same-netns ownership inconsistency, but modification of protected state belonging to another security principal is not demonstrated.
* No common networking data-path bonus was awarded. Triggering requires a rtnetlink control-plane change rather than ordinary packet traffic.
* No V33 Important candidate was retained. Although active registration state and a downstream receive lookup are identified, no credible unresolved guest-to-host, namespace-to-host, or delegated-interface security boundary is established.
* No B5-R condition applies because there is no heap OOB write or retry-accumulated offset.
* No B3-PENDING condition applies because no shared file-backed storage write is involved.
* No B4 authorization profile applies because the existing capability check is not bypassed and the new check enforces state-transition validity rather than access authorization.
3. Reachability analysis
The trigger is a local rtnetlink `changelink` request against an existing GRE, GRETAP, or ERSPAN device. The caller must satisfy `rtnl_dev_link_net_capable()` for the device and tunnel network namespace, which is a namespace-aware `CAP_NET_ADMIN` requirement.
A delegated network-management process or namespace administrator can therefore reach the operation without possessing full host-administrator powers. The complete demonstrated effect remains within the same network namespace. Affecting host-network devices would require authority over the host network namespace.
The attacker must have an existing tunnel device and another metadata device of the same type in that namespace. No special hardware, race, packet timing, boot option, or remote traffic trigger is required. Ordinary packets cannot independently enable `collect_md`.
4. Primitive and severity interpretation
The exact primitive is an invalid active registration transition. A non-metadata tunnel can be converted through `changelink` without the uniqueness enforcement used by `newlink`, replacing a shared metadata receive entry that another device owns. Later deletion can clear that entry and disable lookup for the surviving device.
This is CLASS_C invalid-state and service-disruption behavior. It is not a lifetime violation because no freed object or stale post-lifetime dereference is established. It is also not an authorization bypass because `CAP_NET_ADMIN` validation remains present and the fix adds a state-transition restriction rather than restoring a missing authority check.
The demonstrated consequence is disruption of GRE metadata receive processing in one network namespace. Cross-namespace packet interception, host corruption, panic, disclosure, protected-state modification, and privilege escalation are unsupported. ImportantCandidate is therefore NO, and automatic downgrade is allowed.
5. One-sentence report phrase
A namespace administrator could use the GRE changelink path to violate metadata tunnel uniqueness, replace a shared receive registration, and later disrupt metadata packet lookup for another tunnel in the same network namespace.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a namespace-scoped control-plane logic error with limited service disruption, but no memory corruption, authorization bypass, host boundary crossing, or unresolved Important-preserving primitive.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ip_gre: Reject enabling collect metadata through changelink [ Upstream
Commit: c80315da84998b69b8829785a174b0bf72a81992
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c80315da84998b69b8829785a174b0bf72a81992
Changed files:
net/ipv4/ip_gre.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=c80315da84998b69b8829785a174b0bf72a81992
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98569 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98569
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:L
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
The Best / paranoid CVSS score: 5.3
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: 1
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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