[CVE-2026-68386][LOW] bpf, sockmap: Reject unhashed UDP sockets on sockmap update [ Upstream

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

CVE: CVE-2026-68386
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf, sockmap: Reject unhashed UDP sockets on sockmap update [ Upstream
Commit: 7ffe529e7127411806c8692fb1490f552c629dc2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ffe529e7127411806c8692fb1490f552c629dc2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68386
Analysis date: Mon, 10 Aug 2026 17:12:20 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A BPF sockmap refcounting bug can leak UDP socket objects when an unhashed socket is looked up before bind and later released after its refcounting mode changes, causing potential local resource exhaustion DoS.

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

The original Linux kernel CVE announcement for CVE-2026-68386 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68386

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: LOW
Manual review required: NO

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-2026-68386	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A refcounting logic bug in BPF sockmap handling can leak UDP socket objects. Sockmap accepts unhashed UDP sockets, and a BPF program can take an extra reference through lookup while the socket is still unbound. If the same socket is then bound, its refcounting mode changes and bpf_sk_release can skip the matching decrement, leaving the socket object permanently referenced. For the CVSS the PR:L is used for the paranoid score because a local user or service with delegated BPF and sockmap capabilities may be able to exercise the affected path without full host root. The issue is not network reachable by packet traffic and requires local control of BPF sockmap operations. Impact is resource exhaustion denial of service through repeated socket leaks. No confidentiality or integrity impact is assigned because the primitive is a reference leak rather than UAF, OOB access, or arbitrary write.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	REMOTE BPF LEAK  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Real lifetime corruption: +1. The bug is a refcount lifetime mismatch where a UDP socket reference acquired through BPF sockmap lookup is not released after the socket transitions from unbound to bound.
* Availability impact realistic: +1. Repeated triggering can leak socket objects and may eventually cause memory pressure or resource exhaustion.
* Requires admin/root/CAP_* in typical deployments: -2. BPF sockmap operations normally require privileged BPF and network capabilities in hardened product configurations.

Conservative total: 0.

Paranoid signals:

* Real lifetime corruption: +1. This is still a kernel object lifetime accounting bug, even though it is a leak rather than UAF.
* Availability impact realistic: +1. Sustained abuse can plausibly exhaust kernel memory over time.
* No full privileged penalty in paranoid interpretation: 0. If BPF and sockmap capabilities are delegated to a service account, container root, or reduced-capability process, the attacker may not be equivalent to full host root.

Paranoid total: 2.

Not counted:

* No remote/network-triggerable signal. Packet traffic alone does not trigger this. The attacker needs local BPF sockmap control.
* No generic memory corruption. The patch and commit describe a refcount leak, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation plausible signal. There is no reclaim, object replacement, callback control, type confusion, or write primitive.
* No confidentiality or integrity impact. The primitive is resource leakage only.

## 3. Reachability analysis

The bug is reachable through local BPF sockmap operations involving UDP sockets. In typical hardened deployments, loading and using the required BPF program and sockmap functionality requires CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or equivalent privileged setup, so conservative scoring treats this as privileged local only.

Namespaces or containers may lower the practical barrier if BPF or network administration is delegated to a less trusted service or container root, but that is configuration-dependent. The path is not directly reachable by remote UDP traffic and does not appear to be exploitable by an unauthenticated network peer.

Call-site confidence: medium. The commit clearly describes the lookup and bpf_sk_release refcount mismatch, but only the state validation helper diff is provided.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like kernel resource leak, not an Important-class vulnerability. The theoretical impact is resource exhaustion through repeated leaked socket objects. Realistic exploitation evidence supports DoS only, with no demonstrated memory corruption, information disclosure, privilege escalation, or security-boundary bypass.

The paranoid score remains low because even under delegated BPF access the primitive is still only a socket refcount leak.

## 5. One-sentence report phrase

A BPF sockmap refcounting bug can leak UDP socket objects when an unhashed socket is looked up before bind and later released after its refcounting mode changes, causing potential local resource exhaustion DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED.

This is a privileged or delegated-local BPF resource leak with no evidence of UAF, overwrite, type confusion, remote reachability, or privilege escalation.

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

Patch: bpf, sockmap: Reject unhashed UDP sockets on sockmap update [ Upstream
Commit: 7ffe529e7127411806c8692fb1490f552c629dc2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ffe529e7127411806c8692fb1490f552c629dc2

Changed files:
  net/core/sock_map.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=7ffe529e7127411806c8692fb1490f552c629dc2

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

The original Linux kernel CVE announcement for CVE-2026-68386 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68386

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:N/I:N/A:L
  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: 0
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).