[CVE-2026-68399][MODERATE 7.0] bpf: Fix UAF in sock clone early bailouts [ Upstream

[CVE-2026-68399][MODERATE 7.0] bpf: Fix UAF in sock clone early bailouts [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68399
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf: Fix UAF in sock clone early bailouts [ Upstream
Commit: 14b49b5ab29979552c219a09e569b424fbbf4a6e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=14b49b5ab29979552c219a09e569b424fbbf4a6e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68399
Analysis date: Mon, 10 Aug 2026 16:36:27 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A UAF in BPF socket local storage can occur when `sk_clone()` shallow copies `sk_bpf_storage` and then exits through an early bailout before proper clone initialization, allowing cleanup of the failed clone to free storage still referenced by the parent socket.

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

The original Linux kernel CVE announcement for CVE-2026-68399 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68399

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-68399	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-362;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in the BPF socket local storage path because sk_clone first shallow copies sk_bpf_storage from the parent socket into the cloned socket. If sk_clone then exits through an early bailout before bpf_sk_storage_clone runs, freeing the cloned socket can release BPF local storage that still belongs to the parent socket. The parent socket may then keep a stale pointer to freed BPF storage, creating a memory corruption candidate rather than a simple crash-only bug. For the CVSS the PR:L value is used because practical triggering requires a local user or local process context able to create the relevant socket activity and hit the early bailout conditions, or a system where BPF socket storage is already configured. The issue is not scored as directly network reachable because reliable triggering depends on local BPF storage state and failure conditions, even though socket clone paths can be exercised by network facing workloads. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality and integrity impact due to use-after-free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	REMOTE INIT BPF UAF  KPANIC INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

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

Conservative signals:

* Generic memory corruption, strong corruption primitive: +2. The patch explicitly fixes a UAF where a cloned socket can free BPF local storage still owned by the parent socket.
* Real lifetime corruption: +1. The bug is a socket lifetime and ownership error after shallow copying `sk_bpf_storage`.
* Reliable kernel crash / strong DoS: +1. A stale parent socket pointer to freed BPF storage can plausibly crash the kernel on later access.
* Common networking core path or socket lifetime path: +1. The affected code is in `sk_clone()` and socket destruction paths, although the vulnerable state depends on BPF socket local storage.
* Hard or special trigger condition: -1. Triggering requires an early bailout before `bpf_sk_storage_clone()`, such as failure in `sk_filter_charge()`, and a socket that already has BPF local storage.

Paranoid additional signal:

* Weak LPE concern: +1. The stale pointer remains on a live parent socket and may later be reached through BPF socket storage operations, so privilege escalation cannot be dismissed without manual source review. No stronger LPE score is assigned because the patch does not show attacker-controlled reclaim, controlled replacement, callback control, or arbitrary write.

Not counted:

* Remote reachable: +0. The issue is not scored as directly network-triggerable.
* Local unprivileged high-control BPF API: +0. Unprivileged BPF is disabled or privileged in the evaluated configuration.
* Confidentiality / Integrity direct impact: +0 conservatively. The patch proves UAF, not a concrete read/write primitive.
* Requires admin/root/CAP penalty: not applied as a full -2 in the main score because a system may already have privileged BPF socket storage configured, after which lower-privileged local socket activity may hit the vulnerable clone path. If the product requires the attacker to personally load or attach BPF programs, the practical score drops toward 3-4.

Call-site confidence: high. The commit describes the relevant call sequence: `sock_copy()` shallow copies the pointer, early bailout skips `bpf_sk_storage_clone()`, and `sk_free()` / `__sk_destruct()` / `bpf_sk_storage_free()` frees the wrong storage object.

## 3. Reachability analysis

The realistic trigger is local or workload-adjacent, not purely remote. The system must have `CONFIG_BPF_SYSCALL` and BPF socket local storage in use. In products where unprivileged BPF is disabled, an attacker normally cannot set up the vulnerable BPF state alone without privileges such as CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or an administrator-provided BPF policy.

Namespaces and containers matter. A container or reduced-capability service may be able to create socket activity under an already configured BPF policy, but it usually cannot load the BPF program itself. Therefore PR is best treated as local low-privileged in the paranoid operational model, but privileged setup is a major reachability constraint.

The path is not default-exposed on all systems. It becomes relevant on systems using BPF socket local storage together with socket clone paths and error conditions during clone.

## 4. Severity interpretation

This is more than an ordinary Moderate because the patch fixes a real UAF in core socket lifetime handling. It is not merely a warning, leak, or NULL dereference.

Conservatively, the demonstrated impact is local DoS plus memory corruption, with limited evidence for exploitability beyond crash. Paranoid triage should keep it as an Actionable Moderate / Strong Important candidate because UAF on a live parent socket object can be security-relevant and should not be auto-closed without manual review.

## 5. One-sentence report phrase

A UAF in BPF socket local storage can occur when `sk_clone()` shallow copies `sk_bpf_storage` and then exits through an early bailout before proper clone initialization, allowing cleanup of the failed clone to free storage still referenced by the parent socket.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: the patch explicitly fixes a UAF in socket/BPF lifetime management, and the stale pointer remains attached to a live parent socket. The realistic trigger is constrained by BPF configuration and early bailout conditions, but the memory corruption class is strong enough to require manual review.

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

Patch: bpf: Fix UAF in sock clone early bailouts [ Upstream
Commit: 14b49b5ab29979552c219a09e569b424fbbf4a6e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=14b49b5ab29979552c219a09e569b424fbbf4a6e

Changed files:
  net/core/bpf_sk_storage.c
  net/core/sock.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=14b49b5ab29979552c219a09e569b424fbbf4a6e

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

The original Linux kernel CVE announcement for CVE-2026-68399 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68399

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:L/UI:N/S:U/C:L/I:L/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: 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).