[CVE-2026-64025][MODERATE 7.0] bpf, skmsg: fix verdict sk_data_ready racing with ktls rx [ Upstream

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

CVE: CVE-2026-64025
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf, skmsg: fix verdict sk_data_ready racing with ktls rx [ Upstream
Commit: c9ea01768903ae47f210cd457af1dead6de7a9c3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9ea01768903ae47f210cd457af1dead6de7a9c3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64025
Analysis date: Sun, 19 Jul 2026 12:15:00 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A use-after-free in the BPF sockmap verdict data-ready path can occur when kTLS RX owns the same receive queue, allowing network data arrival on an already configured kTLS sockmap socket to trigger skb lifetime corruption and a kernel crash, with broader impact requiring manual review.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64025 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64025

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-2026-64025	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '8.1';DESCR 'A use-after-free can occur in the BPF sockmap skmsg verdict data-ready path when kTLS RX also owns the same receive queue. If a socket is placed into a sockmap before TLS RX is configured, sk_psock_verdict_data_ready() can run as the saved TLS data-ready callback and drain sk_receive_queue without advancing copied_seq, leaving stale state for the TLS strparser. Later TLS receive processing can walk a frag_list that points to a psock-owned and potentially freed skb, causing kernel memory corruption or a crash. For the CVSS the PR:N is used in the paranoid score because a remote peer may only need network reachability to an already configured vulnerable kTLS and sockmap endpoint. The issue is network reachable in such deployments, although the affected configuration is specific and non-default. Impact is at least denial of service and, because the bug is an explicit use-after-free in network receive processing, privilege escalation or broader confidentiality and integrity impact should be manually reviewed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	REMOTE LOCK BPF UAF LINUS  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2
  Data arrival on an already configured kTLS plus sockmap socket can enter the vulnerable receive path.

* Generic memory corruption, strong primitive: +2
  The commit explicitly describes a use-after-free where `tls_decrypt_sg()` walks a `frag_list` pointing to a psock-owned and potentially freed skb.

* Real lifetime corruption: +1
  This is an skb ownership and lifetime bug between kTLS RX strparser and BPF sockmap verdict handling.

* Reliable kernel crash / strong DoS: +1
  The path includes `WARN_ON_ONCE(!first)` and then a UAF in TLS decrypt processing, making kernel crash realistic.

* Common networking receive path relevance: +1
  The bug is in `net/core/skmsg.c` and affects socket receive queue handling with kTLS.

* Rare / configuration-dependent path: -1
  Requires a specific combination of BPF sockmap verdict handling and kTLS RX, with sockmap insertion before TLS RX setup.

* Special ordering / race-like condition: -1
  Triggerability depends on the ordering between sockmap insertion, TLS RX configuration, and data arrival.

* BPF privilege gating considered
  Loading and configuring sockmap/BPF is typically privileged. However, once a vulnerable endpoint is already configured, a remote peer may trigger the receive path by sending data, so I do not fully downgrade it to a purely local privileged issue.

## 3. Reachability analysis

The vulnerable state normally requires a privileged local component to configure BPF sockmap verdict handling and kTLS RX on the same socket. In typical product configurations, unprivileged BPF is disabled, so a local unprivileged user should not be assumed able to create the setup.

After that setup exists, the actual fault can be triggered by network data arrival on the affected socket. This makes the runtime trigger plausibly remote in deployments using kTLS with sockmap. The path is not default for ordinary TCP sockets and is not Internet-exposed unless such an endpoint is deployed, but it is still security-relevant for systems using BPF sockmap and kTLS in networking data paths.

Namespaces and containers matter mainly for the setup phase. Container root or delegated BPF/CAP_NET_ADMIN/CAP_BPF environments could reduce the practical privilege barrier, but default host configurations usually keep this privileged.

Call-site confidence: high. The commit message provides the relevant call chain from `tls_data_ready()` through `sk_psock_verdict_data_ready()` to `tls_decrypt_sg()`.

## 4. Severity interpretation

This is not an ordinary Moderate resource leak or WARN-only bug. The patch addresses an explicit UAF in skb receive processing caused by conflicting ownership of the receive queue between kTLS and BPF sockmap.

Realistically demonstrated impact is at least a kernel crash / DoS. Practical privilege escalation is not demonstrated, and there is no shown attacker-controlled reclaim or overwrite primitive. However, because this is a network-reachable skb lifetime UAF in a kernel receive path, broader confidentiality or integrity impact cannot be safely excluded without manual review.

Overall this is Actionable Moderate at minimum and a Strong Important candidate in paranoid triage.

## 5. One-sentence report phrase

A use-after-free in the BPF sockmap verdict data-ready path can occur when kTLS RX owns the same receive queue, allowing network data arrival on an already configured kTLS sockmap socket to trigger skb lifetime corruption and a kernel crash, with broader impact requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit UAF in network receive processing, possible remote trigger after privileged setup, and skb lifetime corruption in a security-sensitive path.

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

Patch: bpf, skmsg: fix verdict sk_data_ready racing with ktls rx [ Upstream
Commit: c9ea01768903ae47f210cd457af1dead6de7a9c3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9ea01768903ae47f210cd457af1dead6de7a9c3

Changed files:
  net/core/skmsg.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=c9ea01768903ae47f210cd457af1dead6de7a9c3

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

The original Linux kernel CVE announcement for CVE-2026-64025 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64025

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:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 8.1

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: 5
  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).