[CVE-2026-68300][MODERATE 7.0] sctp: auth: verify auth requirement when auth_chunk is NULL [ Upstream

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

CVE: CVE-2026-68300
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: sctp: auth: verify auth requirement when auth_chunk is NULL [ Upstream
Commit: ec2e157fc9678a9bc411305a25aec3fd337d7efb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ec2e157fc9678a9bc411305a25aec3fd337d7efb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68300
Analysis date: Mon, 10 Aug 2026 17:18:05 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A remote SCTP peer may bypass SCTP AUTH checks when auth_chunk is NULL, allowing chunks that require authentication to be processed without valid AUTH verification and creating integrity impact against exposed SCTP services.

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

The original Linux kernel CVE announcement for CVE-2026-68300 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68300

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-2026-68300	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L';CWE-287;CWE-306;CWE-345;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N';BEST CVSS score: '8.6';DESCR 'SCTP AUTH verification could be bypassed because sctp_auth_chunk_verify returned success whenever chunk.auth_chunk was NULL. A remote peer can hit this state when AUTH is missing before COOKIE-ECHO or when the receive path cannot keep the AUTH chunk, allowing a chunk that requires authentication to be processed without valid AUTH verification. For the CVSS the PR:N because the attacker only needs network reachability to the SCTP endpoint and does not need a local account on the target. The issue is network reachable when SCTP is exposed and SCTP AUTH is configured for the affected chunk types. Impact is primarily integrity loss because unauthenticated protocol chunks may be accepted. The paranoid score also accounts for limited confidentiality or availability impact from unauthorized association state changes, but this is still an authentication bypass and not memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 6)	YES	DANGER SIMPLEFIX NETWORK LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Triggered signals:

* Remote reachable / network-triggerable: +2
  The affected SCTP receive path can be reached by a remote SCTP peer if the SCTP endpoint is exposed.

* Security-boundary bypass: +2
  The bug bypasses SCTP AUTH enforcement because `sctp_auth_chunk_verify()` returned success when `chunk->auth_chunk` was NULL, even when the chunk type required authentication.

* Integrity impact plausible: +1
  An unauthenticated SCTP chunk that should have been rejected may be accepted and processed, creating protocol state manipulation risk.

* Common networking protocol receive path: +1
  This is in SCTP packet processing, not a local-only ioctl or admin control path.

* Rare/configuration-dependent exposure: -1
  Practical exposure requires SCTP use and an SCTP AUTH policy for affected chunk types. SCTP is less commonly Internet-exposed than TCP/UDP services.

Paranoid-only signal:

* Availability impact plausible: +1
  Unauthorized SCTP association state changes could plausibly disrupt connections or service behavior, although the patch does not show a direct crash or memory corruption primitive.

Not applied:

* Generic memory corruption: +0
  The patch shows an authentication logic bypass, not UAF, OOB, double-free, or type confusion.

* Privilege escalation plausible: +0
  No local privilege escalation primitive is indicated.

* Confidentiality impact: +0 conservative
  No direct information disclosure or sensitive-object access primitive is shown.

## 3. Reachability analysis

A remote SCTP peer can trigger the affected logic when it can reach an SCTP endpoint that uses SCTP AUTH for the relevant chunk types. No local account is required on the target, so PR:N is reasonable for CVSS-style reasoning. The issue is not automatically exposed on all Linux systems because SCTP services and SCTP AUTH policies are deployment-dependent. Containers or network namespaces mainly affect which SCTP endpoints are reachable, but the vulnerable path itself is a network receive path rather than a privileged local management interface.

## 4. Severity interpretation

This behaves like an actionable remote authentication bypass rather than ordinary Moderate. The realistic impact is integrity loss in SCTP protocol handling, with possible service disruption depending on the protected chunks and application behavior. It is not an Important-class memory corruption issue based on the patch alone, because there is no demonstrated UAF, overwrite, reclaim primitive, arbitrary write, or kernel crash path. The paranoid score is higher because a remote AUTH bypass in a transport protocol can have deployment-specific security consequences and should not be auto-closed without checking actual SCTP usage.

## 5. One-sentence report phrase

A remote SCTP peer may bypass SCTP AUTH checks when auth_chunk is NULL, allowing chunks that require authentication to be processed without valid AUTH verification and creating integrity impact against exposed SCTP services.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Remote authentication bypasses are deployment-dependent but security-relevant. Manual review should verify whether SCTP is enabled, whether affected SCTP endpoints are exposed, and whether SCTP AUTH is configured for COOKIE-ECHO or other protected chunk types.

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

Patch: sctp: auth: verify auth requirement when auth_chunk is NULL [ Upstream
Commit: ec2e157fc9678a9bc411305a25aec3fd337d7efb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ec2e157fc9678a9bc411305a25aec3fd337d7efb

Changed files:
  net/sctp/sm_statefuns.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=ec2e157fc9678a9bc411305a25aec3fd337d7efb

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

The original Linux kernel CVE announcement for CVE-2026-68300 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68300

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:L/PR:N/UI:N/S:U/C:N/I:H/A:N
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L
  The Best / paranoid CVSS score: 8.6

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).