[CVE-2026-63914][MODERATE 7.0] xfrm: route MIGRATE notifications to caller's netns

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

CVE: CVE-2026-63914
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: xfrm: route MIGRATE notifications to caller's netns
Commit: bafc7d0774b9bf52909c70ed990bc5ccf7ec4bad
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bafc7d0774b9bf52909c70ed990bc5ccf7ec4bad
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63914
Analysis date: Sun, 19 Jul 2026 17:41:51 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
XFRM MIGRATE notifications were incorrectly multicast in init_net instead of the caller network namespace, exposing IPsec migration metadata across namespace boundaries and breaking per-netns IKE migration handling.

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

The original Linux kernel CVE announcement for CVE-2026-63914 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63914

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-2026-63914	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:L/I:L/A:L';CWE-668;*CWE-200;CWE-284;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.3';DESCR 'XFRM MIGRATE notifications were multicast in init_net even when the migration request originated from a different network namespace. This can expose IPsec migration metadata such as selectors, old and new endpoint addresses, and km_address to listeners in init_net, while the IKE daemon inside the originating namespace may miss its own migration event. For the CVSS the PR:L is used in the paranoid score because a reduced capability container root or delegated service account with CAP_NET_ADMIN in its own network namespace may be able to trigger the affected control plane path. The issue is not directly network reachable and is not a memory corruption bug. Impact is mainly namespace isolation bypass, limited confidentiality exposure, possible limited integrity confusion in user space IKE handling, and availability impact for MOBIKE or address update handling inside non init namespaces.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE DANGER INIT SKB LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH KPANIC INCREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

* Security-boundary bypass with practical sensitive-object access: +2
  MIGRATE notifications from a non-init network namespace are delivered to init_net listeners, violating netns isolation and exposing IPsec/XFRM migration metadata.

* Cross-boundary isolation/policy bypass: +1
  The bug crosses a network namespace boundary and breaks the expected per-netns XFRM/PF_KEY notification model.

* Confidentiality impact plausible: +1
  Selectors, old/new endpoint addresses, and km_address can be disclosed to listeners in init_net.

* Availability impact realistic: +1
  IKE daemons inside non-init netns can miss their own migration notifications, breaking MOBIKE/address-update handling.

* Integrity impact plausible in paranoid interpretation: +1
  A userspace IKE daemon may observe or react to migration events from the wrong namespace, creating limited control-plane confusion.

* Requires CAP_NET_ADMIN in typical deployments: -2 conservative
  Triggering XFRM MIGRATE normally requires privileged XFRM control-plane access.

* Privilege penalty reduced in paranoid score: -1 or 0
  In container or delegated-netns deployments, reduced-capability root or service accounts with CAP_NET_ADMIN in their own namespace are not equivalent to full host root.

No memory corruption, UAF, OOB access, refcount bug, or LPE primitive is indicated by the patch.

## 3. Reachability analysis

The bug is locally triggerable through the XFRM/PF_KEY control plane, not by ordinary network packets. In typical host deployments, the caller needs CAP_NET_ADMIN or equivalent authority to issue XFRM migration operations, so the conservative interpretation is privileged local access. In containerized or delegated network namespace setups, a less trusted namespace administrator may be able to trigger the path, while the resulting notification is incorrectly delivered to init_net listeners. XFRM/IPsec is not universal by default, but it is a core Linux networking security subsystem and should not be treated as an obscure hardware-only path.

## 4. Severity interpretation

This behaves like an actionable Moderate issue, not a memory-corruption Important issue. The main risk is namespace isolation failure and control-plane information exposure, plus broken IKE/MOBIKE behavior inside non-init namespaces. There is no evidence of kernel memory corruption, privilege escalation, arbitrary write, or code execution. However, because it crosses a namespace security boundary and exposes IPsec migration metadata, it should not be auto-closed as a trivial correctness fix.

## 5. One-sentence report phrase

XFRM MIGRATE notifications were incorrectly multicast in init_net instead of the caller network namespace, exposing IPsec migration metadata across namespace boundaries and breaking per-netns IKE migration handling.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Manual review is required because this is a cross-namespace control-plane isolation issue involving IPsec/XFRM metadata, and the practical severity depends on container delegation, CAP_NET_ADMIN exposure, and whether init_net IKE listeners can observe or act on non-init netns migration events.

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

Patch: xfrm: route MIGRATE notifications to caller's netns
Commit: bafc7d0774b9bf52909c70ed990bc5ccf7ec4bad
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bafc7d0774b9bf52909c70ed990bc5ccf7ec4bad

Commit description:

xfrm_send_migrate() in net/xfrm/xfrm_user.c and pfkey_send_migrate()
in net/key/af_key.c both hardcode &init_net for the multicast that
announces a successful XFRM_MSG_MIGRATE / SADB_X_MIGRATE.

XFRM_MSG_MIGRATE arrives on a per-netns NETLINK_XFRM socket, and the
rest of the xfrm/af_key netlink path was made netns-aware in 2008.
The other 14 multicast paths in xfrm_user.c route their event using
xs_net(x), xp_net(xp) or sock_net(skb->sk); only the migrate path
was missed.

Two consequences of the init_net hardcoding:

  1. The notification (selector, old/new endpoint addresses, and the
     km_address) is delivered to listeners on init_net's
     XFRMNLGRP_MIGRATE / pfkey BROADCAST_ALL groups rather than on
     the issuing netns. An IKE daemon running in init_net therefore
     receives migration notifications originating from any other
     netns on the host.

  2. An IKE daemon running inside a non-init netns and subscribed
     to its own XFRMNLGRP_MIGRATE / pfkey groups never receives the
     notification of its own migration. IKEv2 MOBIKE / address-update
     handling inside a netns is silently broken.

Thread struct net through km_migrate() and the xfrm_mgr.migrate
function pointer, drop the &init_net override in xfrm_send_migrate()
and pfkey_send_migrate(), and pass the caller's net (already in
scope in xfrm_migrate() via sock_net(skb->sk)) all the way down.
struct xfrm_mgr is in-tree only and not exported as a stable API,
so the function-pointer signature change is internal.

pfkey_broadcast() is already netns-aware via net_generic(net,
pfkey_net_id) since the pernet conversion. The five other
pfkey_broadcast() callers in af_key.c already pass xs_net(x),
sock_net(sk) or a per-netns net, so this only removes the
&init_net outlier.

Fixes: 5c79de6 ("[XFRM]: User interface for handling XFRM_MSG_MIGRATE")
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: Maoyi Xie <maoyi.xie@ntu.edu.sg>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/xfrm/xfrm_user.c
  net/key/af_key.c
  include/net/xfrm.h
  net/xfrm/xfrm_policy.c
  net/xfrm/xfrm_state.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=bafc7d0774b9bf52909c70ed990bc5ccf7ec4bad

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

The original Linux kernel CVE announcement for CVE-2026-63914 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63914

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:L/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: 4
  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).