[CVE-2026-64569][MODERATE REGULAR] mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n [ Upstream

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

CVE: CVE-2026-64569
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n [ Upstream
Commit: d6eee7cd078aaf9dd75efc801f6c9b608a37cd71
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d6eee7cd078aaf9dd75efc801f6c9b608a37cd71
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64569
Analysis date: Wed, 05 Aug 2026 05:25:59 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like by default, manual review recommended only for affected CONFIG_INET=n builds
Manual review required: YES

Summary:
A local unprivileged user can trigger a NULL pointer dereference in the MPLS RTM_GETROUTE dump validation path on CONFIG_INET=n kernels by omitting RTA_OIF, causing a kernel Oops or DoS without evidence of privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-64569 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64569

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64569	MODERATE	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-20;CWE-754;BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in mpls_valid_fib_dump_req() can occur on CONFIG_INET disabled builds because the RTA_OIF path calls nla_get_u32() with a missing attribute pointer. A local unprivileged user can trigger this through an RTM_GETROUTE dump request for AF_MPLS with strict checking and without RTA_OIF, because rtnetlink permits this GET operation without CAP_NET_ADMIN. For the CVSS the PR:L value is used because local code execution by an unprivileged user is required, but no administrative capability is needed. The issue is not network reachable and is triggered through the local rtnetlink control interface. Impact is denial of service via kernel NULL pointer dereference and possible kernel oops or crash on affected CONFIG_INET disabled kernels.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like by default, manual review recommended only for affected CONFIG_INET=n builds (with actual score 2)	YES	KASAN OOB NULLPTR  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like by default, manual review recommended only for affected CONFIG_INET=n builds**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. RTM_GETROUTE is RTNL_KIND_GET and is permitted without CAP_NET_ADMIN, so a local unprivileged user can reach the path.
* Reliable kernel crash / strong DoS: +1. The commit includes a KASAN NULL pointer dereference and kernel Oops in mpls_valid_fib_dump_req().
* Rare AND difficult-to-reach subsystem/configuration: -1. The issue requires CONFIG_INET=n together with MPLS route dump handling, which is uncommon for typical production Linux systems.

Paranoid delta:

* Availability impact realistic: +1. If the affected configuration is present and kernel policy turns Oops into panic, the local trigger can become a host-wide DoS.

Not counted:

* No remote reachable signal. The trigger is local rtnetlink, not packet-driven network input.
* No generic memory corruption. This is a NULL pointer dereference, not UAF, OOB write, double free, or type confusion.
* No privilege escalation signal. The patch does not indicate attacker-controlled reclaim, overwrite, callback control, refcount takeover, or object confusion.
* No confidentiality or integrity impact. There is no disclosure or write primitive.

## 3. Reachability analysis

A local unprivileged process can trigger the bug by sending an AF_MPLS RTM_GETROUTE dump request with strict checking and without RTA_OIF. CAP_NET_ADMIN is not required because rtnetlink treats RTM_GETROUTE as a GET operation. Network namespaces may make the interface more accessible to containerized local users if MPLS and the relevant rtnetlink family are available inside the namespace. The main limiting factor is configuration: CONFIG_INET=n is unusual, and MPLS must be enabled and reachable in the evaluated kernel.

Call-site confidence: high. The provided trace shows the rtnetlink to mpls_dump_routes to mpls_valid_fib_dump_req path and the exact NULL dereference site.

## 4. Severity interpretation

This behaves like an ordinary Moderate local DoS rather than an Important-class vulnerability. The realistic impact is kernel Oops or crash from a local unprivileged rtnetlink request on a narrow kernel configuration. The theoretical memory-corruption potential is weak because the primitive is a NULL dereference only, with no stale object reuse or attacker-controlled memory access. The issue should not be auto-elevated to Important without evidence of a stronger primitive or broader default exposure.

## 5. One-sentence report phrase

A local unprivileged user can trigger a NULL pointer dereference in the MPLS RTM_GETROUTE dump validation path on CONFIG_INET=n kernels by omitting RTA_OIF, causing a kernel Oops or DoS without evidence of privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended to confirm whether the affected product actually ships CONFIG_INET=n with MPLS enabled. If not, this can be treated as ordinary Moderate or low-priority. If yes, the unprivileged local crash path should be tracked, but the patch does not support Important-class scoring.

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

Patch: mpls: fix NULL deref in mpls_valid_fib_dump_req() on CONFIG_INET=n [ Upstream
Commit: d6eee7cd078aaf9dd75efc801f6c9b608a37cd71
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d6eee7cd078aaf9dd75efc801f6c9b608a37cd71

Changed files:
  net/mpls/af_mpls.c
  net/netlink/af_netlink.c
  net/core/rtnetlink.c
  net/socket.c
  arch/x86/entry/syscall_64.c
  arch/x86/entry/entry_64.S

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=d6eee7cd078aaf9dd75efc801f6c9b608a37cd71

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

The original Linux kernel CVE announcement for CVE-2026-64569 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64569

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: Not available
  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: 1
  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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).