[CVE-2026-72413][MODERATE 7.0] sctp: fix err_chunk memory leaks in INIT handling [ Upstream

[CVE-2026-72413][MODERATE 7.0] sctp: fix err_chunk memory leaks in INIT handling [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72413
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: sctp: fix err_chunk memory leaks in INIT handling [ Upstream
Commit: 94f55994e19e8f0676990b9d5015b58ab6a97e00
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=94f55994e19e8f0676990b9d5015b58ab6a97e00
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72413
Analysis date: Sun, 16 Aug 2026 01:11:35 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
A remote SCTP peer may trigger a kernel memory leak in INIT handling by causing `sctp_verify_init()` to allocate `err_chunk` objects that are not freed on several paths, potentially leading to resource exhaustion denial of service when an SCTP endpoint is exposed.

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

The original Linux kernel CVE announcement for CVE-2026-72413 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72413

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-72413	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '7.5';DESCR 'SCTP INIT handling can leak an err_chunk object when unrecognized parameters cause sctp_verify_init to allocate an error chunk and later paths fail to release it. A remote peer can potentially trigger the leak by sending SCTP INIT or unexpected INIT traffic with unrecognized parameters to a reachable SCTP endpoint. For the CVSS the PR:N is used because no privileges are required beyond network reachability to the SCTP service. The realistic impact is denial of service through memory consumption rather than memory corruption. Confidentiality and integrity impact are not assigned because the patch shows a lost reference resource leak and does not indicate UAF, OOB access, information disclosure, or an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	INIT LEAK ERRORPATH NETWORK LINUS  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: **3**
* Paranoid score: **5**
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: **+2**
  SCTP INIT and unexpected INIT processing are network protocol paths. A remote peer can potentially trigger the leak if an SCTP endpoint is reachable.

* Availability impact realistic: **+1**
  The bug is a memory leak in kernel SCTP chunk handling. Repeated triggering may consume memory and cause service degradation or system DoS.

Conservative non-signals:

* Generic memory corruption: **+0**
  The patch fixes missing `sctp_chunk_free(err_chunk)` calls. This is a lost-reference memory leak, not UAF, double-free, OOB write, type confusion, or arbitrary write.

* Privilege escalation plausible: **+0**
  No reclaim primitive, stale callback, overwrite, refcount takeover, or attacker-controlled object reuse is shown.

* Confidentiality / Integrity impact: **+0**
  No information disclosure or write primitive is supported by the patch.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: **+1**
  If an exposed SCTP service can be repeatedly targeted with INIT packets containing unrecognized parameters, the leak may become a practical resource exhaustion DoS.

* Common networking receive path scrutiny: **+1**
  This is in network protocol receive/state-machine handling, so it deserves more scrutiny than a local-only cleanup leak, even though SCTP exposure is less common than TCP/UDP.

Possible exposure reduction:

* SCTP is not universally enabled or exposed on all systems, but no rare-configuration penalty is applied because the affected path is reachable through ordinary network traffic when SCTP service is in use.

## 3. Reachability analysis

A remote unauthenticated peer can potentially trigger the vulnerable paths by sending SCTP INIT or unexpected INIT traffic with unrecognized parameters to a reachable SCTP endpoint. No local code execution or local user account is required for the network-triggered scenario, so PR:N is reasonable for CVSS-style interpretation.

Namespaces and containers do not materially reduce the remote attack model if the SCTP service is exposed outside the host or container boundary. If SCTP is disabled, blocked by firewall policy, or no SCTP listener exists, practical exposure is much lower.

Realistic exploitation requires repeated triggering to accumulate leaked `err_chunk` objects. A single packet is unlikely to cause immediate system-wide failure, so the conservative score stays below Important.

## 4. Severity interpretation

This behaves like an **actionable Moderate** issue rather than a clear Important vulnerability. The main impact is remote resource exhaustion DoS, not memory corruption or privilege escalation.

The theoretical worst case is kernel memory exhaustion through repeated remote SCTP traffic. The realistic evidence supports a leak and potential DoS, but not UAF, arbitrary write, information disclosure, or LPE.

## 5. One-sentence report phrase

A remote SCTP peer may trigger a kernel memory leak in INIT handling by causing `sctp_verify_init()` to allocate `err_chunk` objects that are not freed on several paths, potentially leading to resource exhaustion denial of service when an SCTP endpoint is exposed.

## 6. Manual review recommendation

**MANUAL CHECK RECOMMENDED**

Reason: network reachability makes this unsuitable for automatic closure, but the patch shows a resource leak only, with no concrete memory corruption or privilege escalation primitive.

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

Patch: sctp: fix err_chunk memory leaks in INIT handling [ Upstream
Commit: 94f55994e19e8f0676990b9d5015b58ab6a97e00
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=94f55994e19e8f0676990b9d5015b58ab6a97e00

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=94f55994e19e8f0676990b9d5015b58ab6a97e00

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

The original Linux kernel CVE announcement for CVE-2026-72413 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72413

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:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 7.5

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: 3
  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: NO
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).