[CVE-2026-68315][MODERATE 7.0] sctp: validate stream count in sctp_process_strreset_inreq() [ Upstream

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

CVE: CVE-2026-68315
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: sctp: validate stream count in sctp_process_strreset_inreq() [ Upstream
Commit: b255d8cd6cc68045ae9eecbac3b3c14e1f176c9b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b255d8cd6cc68045ae9eecbac3b3c14e1f176c9b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68315
Analysis date: Mon, 10 Aug 2026 17:29:34 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
An SCTP peer can trigger a `__u16` size overflow while processing stream reset requests on high-MTU or IPv6 jumbogram-capable paths, leading to an undersized skb allocation and kernel BUG DoS, with no proven arbitrary write or privilege-escalation primitive.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68315 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68315

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-2026-68315	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-190;CWE-131;CWE-617;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'An SCTP peer can send a RESET_IN_REQUEST with a stream list that fits the incoming parameter but would make the generated RESET_OUT_REQUEST exceed SCTP_MAX_CHUNK_LEN. The OUT request header is larger than the IN request header, so on paths that can carry payloads above 65535 bytes (for example loopback with IPv6 jumbograms) the size calculation in sctp_make_strreset_req can overflow a 16 bit value and allocate an undersized skb. This leads to skb_put or skb_panic and a kernel crash. For the CVSS the PR:N is used because the peer does not need privileges on the target beyond SCTP reachability. AV:A and AC:H are used because reliable triggering depends on a nonstandard high MTU or jumbogram capable path rather than normal Internet exposure. Impact is denial of service via kernel crash. The paranoid score keeps C:L and I:L because the bug class includes integer overflow and undersized allocation in network packet construction, but the observed primitive is still a checked skb BUG rather than a proven arbitrary write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	DANGER NETWORK SKB IPV6 KPANIC 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  SCTP peer input can reach `sctp_process_strreset_inreq()`, but practical triggering requires unusual packet size conditions.

* Constrained kernel buffer overwrite / undersized allocation candidate: +1
  The bug is a `__u16` size overflow that can allocate an undersized skb before `skb_put()` detects the overflow and hits `skb_panic`.

* Memory layout invariant restoration: +1
  The patch restores consistency between incoming `RESET_IN_REQUEST` sizing and the larger generated `RESET_OUT_REQUEST` sizing.

* Reliable kernel crash / strong DoS: +1
  The commit provides a concrete crash path ending in `skb_panic` / kernel BUG.

* Hard or special triggering condition: -1
  Normal IP payload limits usually prevent the oversized stream list. Triggering requires MTU above 65535, such as loopback with IPv6 jumbograms.

* Corruption primitive constrained / no proven attacker-controlled target: -1
  The described failure is an undersized skb followed by checked skb bounds failure, not a demonstrated arbitrary write or UAF reclaim primitive.

* Rare or difficult-to-reach runtime condition: -1
  SCTP itself is less common than TCP/UDP, and the jumbogram or high-MTU condition further narrows exposure.

Paranoid adjustment:

* Additional network packet-construction scrutiny: +1
  This is still a peer-controlled protocol parsing path with integer overflow and undersized skb allocation in kernel networking code, so it should not be auto-closed without review.

## 3. Reachability analysis

An SCTP peer can trigger the vulnerable path by sending a crafted `RESET_IN_REQUEST` whose stream list fits the incoming parameter but causes the generated `RESET_OUT_REQUEST` to exceed `SCTP_MAX_CHUNK_LEN`. No privileges on the target are required beyond SCTP reachability.

The main limiting factor is transport size. The commit states that ordinary IP payload limits normally prevent this, and practical triggering requires interfaces or paths supporting payloads above 65535 bytes, for example loopback with IPv6 jumbograms. This makes Internet-scale remote exploitation unlikely, but local, adjacent, or special network setups remain relevant.

Namespaces may matter if an unprivileged user can create or access SCTP associations over loopback or a controlled network namespace with suitable MTU configuration. In typical deployments, SCTP and IPv6 jumbogram style paths are not broadly exposed by default.

Call-site confidence: high. The patch and commit include the affected function, the generated response path, and the concrete crash stack through `sctp_make_strreset_req()`, `sctp_addto_chunk()`, `skb_put()`, and `skb_panic`.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an ordinary low-priority Moderate. The realistic demonstrated impact is DoS via kernel BUG, not proven privilege escalation.

The theoretical memory corruption concern comes from integer overflow and undersized skb allocation in network packet construction. However, the commit evidence points to a checked skb panic rather than attacker-controlled overwrite, UAF, object replacement, or arbitrary write. Therefore Important-class treatment is not justified from the patch alone, but manual review is appropriate because it is a peer-triggerable networking bug with a concrete kernel crash path.

## 5. One-sentence report phrase

An SCTP peer can trigger a `__u16` size overflow while processing stream reset requests on high-MTU or IPv6 jumbogram-capable paths, leading to an undersized skb allocation and kernel BUG DoS, with no proven arbitrary write or privilege-escalation primitive.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: peer-controlled networking input reaches an integer overflow and undersized skb allocation path with a concrete kernel crash. The unusual MTU requirement lowers practical exposure, but the combination of SCTP protocol reachability, skb construction, and kernel BUG makes this unsuitable for automatic closure.

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UPSTREAM PATCH SUMMARY
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Patch: sctp: validate stream count in sctp_process_strreset_inreq() [ Upstream
Commit: b255d8cd6cc68045ae9eecbac3b3c14e1f176c9b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b255d8cd6cc68045ae9eecbac3b3c14e1f176c9b

Changed files:
  net/core/skbuff.c
  net/sctp/sm_make_chunk.c
  net/sctp/stream.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=b255d8cd6cc68045ae9eecbac3b3c14e1f176c9b

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

The original Linux kernel CVE announcement for CVE-2026-68315 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68315

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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.4

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).