[CVE-2026-68320][IMPORTANT] sctp: fix auth_chunk_list capacity check in sctp_auth_ep_add_chunkid [ Upstream

[CVE-2026-68320][IMPORTANT] sctp: fix auth_chunk_list capacity check in sctp_auth_ep_add_chunkid [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68320
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: sctp: fix auth_chunk_list capacity check in sctp_auth_ep_add_chunkid [ Upstream
Commit: 5a365f1e423444c5da7eb689a8661633dad43e48
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5a365f1e423444c5da7eb689a8661633dad43e48
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68320
Analysis date: Mon, 10 Aug 2026 14:08:48 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local SCTP user can configure too many SCTP-AUTH chunk IDs, causing `sctp_association_init()` to copy up to 4 bytes past `asoc->c.auth_chunks`, which creates a kernel out-of-bounds write with at least DoS impact and possible local privilege escalation risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68320 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68320

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: IMPORTANT
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-2026-68320	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-131;CWE-120;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'An out-of-bounds write can occur in the SCTP-AUTH endpoint configuration path because sctp_auth_ep_add_chunkid() used SCTP_NUM_CHUNK_TYPES as the capacity limit for ep auth_chunk_list while the later cookie destination asoc c auth_chunks has room for only SCTP_AUTH_MAX_CHUNKS entries. A local user can create or control an SCTP socket and add more than 16 authenticated chunk IDs, after which association initialization copies the oversized list and can overflow the destination by up to 4 bytes. For the CVSS the PR:L value is used because reliable triggering requires a local user or process able to use the SCTP socket interface and configure SCTP-AUTH chunks. The issue is not directly network reachable for an unauthenticated remote attacker because the oversized endpoint list is created through local socket configuration, although network activity may help reach association setup after the local state is prepared. Impact is at least denial of service and may include confidentiality or integrity impact because the patch context shows a real kernel out-of-bounds write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	SIMPLEFIX NETWORK LINUS KPANIC 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process can plausibly create or control an SCTP socket and configure SCTP-AUTH chunk IDs.
* Constrained kernel buffer overwrite: +1. The overflow is explicit, but limited to up to 4 bytes into a fixed destination in `struct sctp_cookie`.
* Weak LPE concern: +1. Kernel memory corruption exists, but the patch does not show attacker-controlled target selection, reclaim, callback control, or an arbitrary write primitive.
* Reliable kernel crash / strong DoS: +1. A kernel-side out-of-bounds write during association initialization can realistically crash or corrupt state.
* Confidentiality impact plausible: +1. Because this is kernel memory corruption, limited information impact cannot be excluded without manual layout analysis.
* Integrity impact plausible: +1. A real write past the destination buffer gives at least limited integrity concern.

Paranoid elevation:

* Strong corruption primitive instead of constrained overwrite: +2 instead of +1. The bug is a real kernel OOB write caused by copying an oversized authenticated chunk list into a smaller cookie field.
* Privilege escalation plausible: +2 instead of +1. For paranoid triage, a local kernel OOB write in networking state is a defensible LPE candidate even if the write is small.

Not counted:

* Remote reachable: +0. The oversized endpoint auth chunk list appears to be created through local SCTP socket configuration, not by an unauthenticated remote packet alone.
* Common networking core path: +0. SCTP is a networking protocol, but not a central TCP/IP or generic packet-processing path.
* Hard race penalty: 0. This is not race-dependent.
* Requires admin/root/CAP penalty: 0. Basic SCTP socket usage is not inherently CAP_SYS_ADMIN or CAP_NET_ADMIN in typical configurations, although product hardening may restrict it.

## 3. Reachability analysis

The likely trigger is a local user or local process able to create an SCTP socket and configure SCTP-AUTH chunk IDs so that more than `SCTP_AUTH_MAX_CHUNKS` entries are stored. The overflow occurs later when `sctp_association_init()` copies the endpoint list into `asoc->c.auth_chunks`, whose destination capacity is smaller.

This is not best treated as unauthenticated remote network reachability. A remote peer may be involved in reaching association setup, but the vulnerable oversized local endpoint state is created through the local socket API. Network namespaces or containers may matter if untrusted workloads are allowed to create SCTP sockets and the SCTP module is available on the host. SCTP is not universally deployed or loaded by default, but it remains reachable through an ordinary local networking interface when enabled.

Call-site confidence: medium. The commit explicitly names the downstream copy in `sctp_association_init()` and the destination object, but the full surrounding caller code is not included in the pasted patch.

## 4. Severity interpretation

This should not be auto-closed as an ordinary Moderate. The realistic impact is at least local DoS through kernel memory corruption. The theoretical worst case is local privilege escalation, because the patch fixes a concrete kernel out-of-bounds write rather than a validation-only warning or bookkeeping mismatch.

The main limiting factors are the small overflow size, fixed destination context, and lack of demonstrated target control or exploit chain. Those factors keep the conservative score at Actionable Moderate. The paranoid score reaches Strong Important candidate because local kernel OOB writes in networking state historically require manual review even when the initial visible overwrite is small.

## 5. One-sentence report phrase

A local SCTP user can configure too many SCTP-AUTH chunk IDs, causing `sctp_association_init()` to copy up to 4 bytes past `asoc->c.auth_chunks`, which creates a kernel out-of-bounds write with at least DoS impact and possible local privilege escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a concrete kernel OOB write, not just resource exhaustion or a WARN. The overwrite is small and constrained, but because it occurs in kernel networking association state and may be locally reachable by unprivileged users, it should receive manual exploitability and structure-layout review.

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

Patch: sctp: fix auth_chunk_list capacity check in sctp_auth_ep_add_chunkid [ Upstream
Commit: 5a365f1e423444c5da7eb689a8661633dad43e48
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5a365f1e423444c5da7eb689a8661633dad43e48

Changed files:
  net/sctp/auth.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=5a365f1e423444c5da7eb689a8661633dad43e48

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

The original Linux kernel CVE announcement for CVE-2026-68320 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68320

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 6
  Paranoid ActionableScore: 8

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).