[CVE-2026-68161][MODERATE 7.0] sctp: close UDP tunnel sockets during netns teardown [ Upstream

[CVE-2026-68161][MODERATE 7.0] sctp: close UDP tunnel sockets during netns teardown [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68161
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: sctp: close UDP tunnel sockets during netns teardown [ Upstream
Commit: c6eb2d615210b80339548ab07c0230edaab9a6c7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6eb2d615210b80339548ab07c0230edaab9a6c7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68161
Analysis date: Mon, 10 Aug 2026 09:34:20 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
SCTP UDP tunnel sockets created through `net.sctp.udp_port` were not stopped during network namespace teardown, allowing stale per-net socket lifetime that can cause local DoS and may warrant manual review for possible UAF-like stale references.

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

The original Linux kernel CVE announcement for CVE-2026-68161 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68161

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-2026-68161	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-404;CWE-362;*CWE-416;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'SCTP per-net UDP tunnel sockets can remain installed while the network namespace is being torn down because the netns exit path did not stop sockets created through net.sctp.udp_port. This can leave stale socket lifetime relative to per-net SCTP teardown and may cause resource leakage, teardown hangs, or in the worst grounded case stale references during destruction. For the CVSS the PR:L is used because reliable triggering requires local code execution with the ability to create or control a network namespace and write the SCTP sysctl, which can be available to an unprivileged local user when user namespaces are enabled. The issue is not directly network reachable through packet traffic. Impact is at least local denial of service. In the paranoid interpretation it may allow limited confidentiality or integrity impact due to a possible stale reference or use-after-free pattern, but the primary expected impact is availability.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	SIMPLEFIX NETWORK LINUS KPANIC  KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS 	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  Triggering requires local code execution and the ability to create/control a network namespace and write `net.sctp.udp_port`. On systems with unprivileged user namespaces enabled, this can be reachable by an unprivileged local user via CAP_NET_ADMIN inside the created namespace.

* Real lifetime corruption: +1
  SCTP UDP tunnel sockets can outlive the network namespace teardown path that should have stopped them, creating a real per-net resource lifetime mismatch.

* Reliable kernel crash / strong DoS or teardown DoS concern: +1
  The bug can leave sockets installed during namespace destruction, plausibly causing teardown hangs, resource leakage, or later invalid lifetime interactions.

* Cross-boundary isolation/resource concern: +1
  The issue is tied to namespace teardown and per-net resources, so a namespace-local action may affect host-level resource cleanup or kernel lifetime state.

Paranoid additional signal:

* Memory corruption, weak/indirect corruption candidate: +1
  The patch prevents sockets from surviving past related per-net/control-socket teardown. This is a stale-lifetime pattern that may imply possible stale references or UAF-like behavior, but the patch does not show attacker-controlled reclaim, overwrite, callback control, or type confusion.

Negative signals:

* No remote reachable signal.
  This is not triggered by SCTP packets alone.

* No strong LPE signal.
  There is no demonstrated reclaim, controlled object replacement, arbitrary write, or callback hijack.

* No hard race subtraction applied.
  The main issue appears to be a deterministic teardown omission rather than a narrow timing-only race, although sysctl writes are explicitly ordered out by unregistering first.

## 3. Reachability analysis

The realistic trigger is local. An attacker needs to arrange a network namespace with SCTP UDP tunneling enabled through `net.sctp.udp_port`, then tear down the namespace while the per-net SCTP UDP tunnel sockets exist. In traditional deployments this may require CAP_NET_ADMIN, but user namespaces can lower the practical privilege requirement because a local unprivileged user may obtain CAP_NET_ADMIN inside a newly created network namespace if unprivileged user namespaces are enabled.

The path is not directly network-triggerable through packet traffic. SCTP itself is a networking subsystem, but the vulnerable condition is in netns cleanup and sysctl-controlled socket lifetime management. Exploitation conditions are plausible for local namespace-capable users, but there is no evidence in the patch of a reliable privilege-escalation primitive.

Call-site confidence: medium. The patch context shows the teardown site and ordering relative to sysctl unregister and control socket destruction, but does not include deeper users of the stale UDP tunnel sockets after teardown.

## 4. Severity interpretation

This is stronger than an ordinary cleanup bug because it affects per-net socket lifetime during namespace teardown. The conservative behavior is local DoS or resource/lifetime cleanup failure. The paranoid interpretation treats the remaining sockets as a possible weak stale-reference or UAF candidate, but without a demonstrated corruption sink.

This should not be classified as Important on the available evidence. It is best handled as Actionable Moderate at minimum because namespace lifetime bugs can be underestimated and should not be auto-closed without confirming whether stale sockets can be reached after related SCTP per-net structures are destroyed.

## 5. One-sentence report phrase

SCTP UDP tunnel sockets created through `net.sctp.udp_port` were not stopped during network namespace teardown, allowing stale per-net socket lifetime that can cause local DoS and may warrant manual review for possible UAF-like stale references.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch fixes a namespace teardown lifetime bug involving sockets and per-net SCTP state, and although the demonstrated impact is mainly DoS/resource cleanup failure, the stale lifetime pattern is close enough to UAF-class issues to require manual confirmation.

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

Patch: sctp: close UDP tunnel sockets during netns teardown [ Upstream
Commit: c6eb2d615210b80339548ab07c0230edaab9a6c7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6eb2d615210b80339548ab07c0230edaab9a6c7

Changed files:
  net/sctp/protocol.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=c6eb2d615210b80339548ab07c0230edaab9a6c7

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

The original Linux kernel CVE announcement for CVE-2026-68161 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68161

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:L/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:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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).