[CVE-2026-68415][MODERATE 7.0] xfrm: clear mode callbacks after failed mode setup [ Upstream

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

CVE: CVE-2026-68415
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: xfrm: clear mode callbacks after failed mode setup [ Upstream
Commit: 9845a35986a658816f7752f7ebd7c455a4c7dfdf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9845a35986a658816f7752f7ebd7c455a4c7dfdf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68415
Analysis date: Mon, 10 Aug 2026 12:22:02 -0400
ActionableScore: 6
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A failed XFRM IPTFS mode setup can leave a stale mode callback pointer in a dead state after the module reference is dropped, allowing deferred GC after module unload to dereference freed module callbacks and crash the kernel, with a paranoid concern for memory-corruption impact.

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

The original Linux kernel CVE announcement for CVE-2026-68415 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68415

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-2026-68415	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-672;CWE-824;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A stale callback pointer can remain in an XFRM state when IPTFS mode initialization or clone fails before mode specific data is published. The temporary module reference is dropped, but the dead state can still carry the cached mode callback table until deferred xfrm_state_gc_task runs after xfrm_iptfs has been unloaded. This creates a use-after-free like condition where GC may dereference callbacks that belong to an unloaded module, leading at least to a kernel crash and denial of service. For the CVSS the PR:L is used in the paranoid score because XFRM control can be delegated to a reduced capability root, container root, or service account with CAP_NET_ADMIN in some deployments, even though typical module unload control is more privileged. The issue is local and not directly network reachable. Impact is at least local denial of service via kernel crash. In the worst still defensible interpretation, the stale callback table after module unload is a memory corruption candidate and may allow confidentiality or integrity impact, so this should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-68415 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 4b3faf610cc63bfac972711635eafbca5e7d7117 YES  NO NO unknown 	MAYBE	INIT LINUS KPANIC 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Generic memory corruption: +2. The state can retain a stale `mode_cbs` callback table pointer after the module reference is dropped and after `xfrm_iptfs` is unloaded.
* Real lifetime corruption: +1. This is a real lifetime mismatch involving a stale pointer surviving past module lifetime into deferred GC.
* Reliable kernel crash / strong DoS: +1. The commit includes a reproduced kernel panic in `xfrm_state_gc_task`.
* Weak LPE concern: +1. Callback-table dereference after module unload is more concerning than a plain NULL dereference, but there is no demonstrated reclaim or controlled replacement primitive.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs in XFRM/IPsec state management and deferred kernel GC.
* Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering usually requires XFRM state control and module unload capability.
* Hard or unreliable race / special condition: -1. The reproduced case requires failed IPTFS setup, ENOMEM or fault injection, deferred GC, and module unload timing.

Conservative total: 3.

Paranoid adjustments:

* Confidentiality impact plausible: +1. If stale module memory is reused in a controlled or partially controlled way, callback-table reuse could theoretically affect reads or control flow.
* Integrity impact plausible: +1. The stale callback pointer is a memory corruption candidate, not just resource exhaustion.
* Privilege penalty reduced: +1 relative to conservative. In some environments XFRM control may be delegated to container root, service accounts, or reduced-capability root with CAP_NET_ADMIN, so treating this only as full host-root is too optimistic.

Paranoid total: 6.

## 3. Reachability analysis

The bug is local and not directly network reachable. A realistic trigger needs XFRM/IPsec state manipulation involving IPTFS mode, a failed mode initialization or clone before `mode_data` is published, and delayed garbage collection after `xfrm_iptfs` has been unloaded.

In typical deployments, creating or modifying XFRM state requires CAP_NET_ADMIN, and unloading the module requires stronger administrative control such as CAP_SYS_MODULE or root-equivalent access. However, XFRM control may be delegated in containerized or service-managed environments, so a reduced-capability root or network-management service account can be relevant for the paranoid interpretation.

The path is not a common packet receive parser, but XFRM/IPsec is a core networking security subsystem and should not be treated as an obscure debug-only path. Exploitation conditions are nontrivial because the demonstrated trigger depends on allocation failure and GC/module-unload ordering.

Call-site confidence: high. The patch and commit describe both the failed setup path and the deferred GC/unload path.

## 4. Severity interpretation

This is stronger than an ordinary Moderate crash because it involves a stale callback pointer retained after the module reference lifetime ends. The demonstrated impact is a local kernel panic, so the conservative score remains limited by privilege requirements and difficult triggering conditions.

The theoretical concern is memory corruption through stale callback-table dereference after module unload. The patch does not demonstrate attacker-controlled reclaim, arbitrary write, or reliable object replacement, so this should not be treated as proven LPE. Still, the callback/lifetime nature makes it an actionable Moderate and a plausible Important candidate for manual review.

## 5. One-sentence report phrase

A failed XFRM IPTFS mode setup can leave a stale mode callback pointer in a dead state after the module reference is dropped, allowing deferred GC after module unload to dereference freed module callbacks and crash the kernel, with a paranoid concern for memory-corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

The issue involves a stale callback pointer after module unload and deferred GC, which is a real lifetime corruption pattern with possible impact beyond DoS even though practical exploitation appears difficult.

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

Patch: xfrm: clear mode callbacks after failed mode setup [ Upstream
Commit: 9845a35986a658816f7752f7ebd7c455a4c7dfdf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9845a35986a658816f7752f7ebd7c455a4c7dfdf

Changed files:
  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=9845a35986a658816f7752f7ebd7c455a4c7dfdf

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

The original Linux kernel CVE announcement for CVE-2026-68415 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68415

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:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 3
  Paranoid ActionableScore: 6

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).