[CVE-2026-53246][IMPORTANT] sctp: validate cached peer INIT chunk length in COOKIE_ECHO processing [ Upstream

[CVE-2026-53246][IMPORTANT] sctp: validate cached peer INIT chunk length in COOKIE_ECHO processing [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53246
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: sctp: validate cached peer INIT chunk length in COOKIE_ECHO processing [ Upstream
Commit: cc272185c9a9a4b7febc2de52eeaa3d00f19091e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc272185c9a9a4b7febc2de52eeaa3d00f19091e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53246
Analysis date: Thu, 25 Jun 2026 10:13:55 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A remote SCTP peer can send a malformed COOKIE_ECHO containing an embedded INIT chunk with an inflated length, causing out-of-bounds parameter parsing and possible memory corruption in the kernel SCTP receive path.

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

The original Linux kernel CVE announcement for CVE-2026-53246 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53246

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
======================================================================

CVE-2026-53246	IMPORTANT	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-125;CWE-130;CWE-119;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '9.8';DESCR 'SCTP COOKIE_ECHO processing can use a cached peer INIT chunk whose header length is larger than the remaining COOKIE_ECHO payload. This allows sctp_process_init() and sctp_walk_params() to walk beyond the actual received buffer and can lead to out-of-bounds reads during later parameter handling such as STATE_COOKIE processing and kmemdup() copies. For the CVSS the PR:N is appropriate because a remote attacker only needs network reachability to a listening SCTP endpoint and does not need a local account on the target. The issue is network reachable over SCTP and is not triggered by a local device or procfs style interface. Impact is at least remote denial of service via kernel crash. In worst case it may allow confidentiality or integrity impact because the bug class is remote memory safety with out-of-bounds parsing and possible memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	OOB DANGER SIMPLEFIX NETWORK LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	NO	NO	checked

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

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:

* Remote reachable / network-triggerable: +2
  A listening SCTP server can process attacker-supplied COOKIE_ECHO chunks over the network.

* Memory corruption, weak/indirect corruption candidate: +1
  The patch fixes missing bounds validation for an embedded INIT chunk length. The described primitive is OOB parameter walking, with possible later unsafe handling, but no direct arbitrary write is demonstrated.

* Reliable kernel crash / strong DoS: +1
  Walking beyond the received buffer in SCTP parsing can realistically lead to kernel fault or crash.

* Confidentiality impact plausible: +1
  The primary concrete primitive is OOB read during parameter parsing.

* Integrity impact plausible: +1
  The commit explicitly mentions potential memory corruption during later parameter handling, including STATE_COOKIE processing and kmemdup copies.

Paranoid additional interpretation:

* Memory corruption, strong corruption primitive: upgraded from +1 to +2
  In the paranoid view, remote protocol parsing of attacker-controlled SCTP chunks with OOB traversal and downstream parameter copying is treated as a strong memory-safety candidate.

* Common protocol receive path scrutiny: +1
  SCTP is less common than TCP/UDP, but this is still a kernel network receive parsing path exposed by a listening endpoint.

No subtraction applied:

* No admin/CAP requirement is needed for a remote peer reaching the SCTP service.
* No hard race or special timing is required.
* No rare hardware or legacy execution mode is required.

## 3. Reachability analysis

The bug is triggerable by a remote peer that can send SCTP traffic to a listening SCTP endpoint. No local account on the victim is required, so PR:N is appropriate for CVSS-style reasoning. Namespaces do not materially reduce the attacker requirement for the network-facing case, although exposure depends on whether SCTP is enabled, loaded, and actually used by a service. SCTP is not universally deployed on Internet-facing systems, but it is a real network protocol path and can be reachable in telecom, clustering, and specialized infrastructure environments.

## 4. Severity interpretation

This is not an ordinary low-risk validation cleanup. The conservative interpretation is an actionable remote DoS with OOB read and plausible integrity impact from malformed protocol parsing. The paranoid interpretation is a Strong Important candidate because the vulnerable path is remotely reachable and the patch context explicitly mentions possible memory corruption during later parameter handling. Practical exploitation beyond crash is not demonstrated, so arbitrary code execution or reliable privilege escalation should not be assumed.

## 5. One-sentence report phrase

A remote SCTP peer can send a malformed COOKIE_ECHO containing an embedded INIT chunk with an inflated length, causing out-of-bounds parameter parsing and possible memory corruption in the kernel SCTP receive path.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a remotely reachable network parser memory-safety issue with OOB read and stated potential memory corruption, so it should not be auto-closed even if the easiest demonstrated impact is DoS.

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

Patch: sctp: validate cached peer INIT chunk length in COOKIE_ECHO processing [ Upstream
Commit: cc272185c9a9a4b7febc2de52eeaa3d00f19091e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cc272185c9a9a4b7febc2de52eeaa3d00f19091e

Changed files:
  net/sctp/sm_make_chunk.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=cc272185c9a9a4b7febc2de52eeaa3d00f19091e

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

The original Linux kernel CVE announcement for CVE-2026-53246 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53246

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 9.8

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).