[CVE-2026-74469][MODERATE 7.0] sctp: prevent peer transport count overflow

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

CVE: CVE-2026-74469
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: sctp: prevent peer transport count overflow
Commit: 546221b86ceeba0d8fec92d46a0604bb7b62be07
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=546221b86ceeba0d8fec92d46a0604bb7b62be07
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74469
Analysis date: Sat, 15 Aug 2026 11:08:45 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
An SCTP transport_count integer overflow can cause sock_diag to under-allocate the INET_DIAG_PEERS payload and then copy many peer addresses past the skb tail, resulting in kernel memory corruption and likely DoS with possible higher impact requiring manual review.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74469 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74469

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-2026-74469	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-190;CWE-131;*CWE-787;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An integer overflow in SCTP peer transport accounting can wrap the 16 bit transport_count after 65535 unique peer transports. SCTP sock_diag then uses the wrapped count to reserve the INET_DIAG_PEERS payload but still copies one sockaddr_storage for every entry in transport_addr_list, causing an skb out of bounds write that can reach about 8 MiB past the tail. The SCTP part can be reached over the network when an SCTP service is exposed, but the corrupting sock_diag dump is normally triggered through a local diagnostic interface. For the CVSS the PR:L is used because reliable exploitation needs a local user or process that can create or influence SCTP associations and request the sock_diag dump, while a malicious peer may supply the large peer address set. The issue is not a simple DoS only bug because the failing operation is an out of bounds kernel write into skb memory. Impact is at least local denial of service and in the paranoid interpretation may allow confidentiality and integrity impact through memory corruption. Manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	OOB SIMPLEFIX NETWORK SKB LINUS KPANIC  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged trigger: +1. The corrupting path is normally reached through a local SCTP sock_diag dump.
* Generic memory corruption, strong corruption primitive: +2. The commit explicitly describes an skb out-of-bounds write up to about 8 MiB past the skb tail.
* Memory layout invariant restoration: +1. The bug is a mismatch between a wrapped allocation/count field and the real transport list copied into the skb payload.
* Weak LPE concern: +1. OOB write into kernel skb memory can plausibly become more than DoS, but no controlled target, reclaim, or reliable overwrite primitive is demonstrated.
* Reliable kernel crash / strong DoS: +1. A large skb tail overwrite is a strong crash candidate.
* Hard or special triggering condition: -1. Reaching 65536 unique SCTP peer transports and then triggering sock_diag is non-trivial.
* Paranoid-only confidentiality impact plausible: +1. Kernel memory corruption may expose data indirectly, but no direct leak is shown.
* Paranoid-only integrity impact plausible: +1. The OOB write can corrupt kernel memory, though target control is not demonstrated.

## 3. Reachability analysis

A local user or local process is the main reliable trigger because the overflow becomes dangerous when SCTP sock_diag builds the diagnostic response. A remote SCTP peer may influence the peer transport set when an SCTP service is exposed, but the final corrupting dump is not purely remote in the provided patch context, so I would not score it as fully AV:N or remote-triggerable for the main actionable score. Namespaces may matter because network namespace delegation and local diagnostic access can make this reachable from less privileged container contexts. SCTP is not as broadly exposed as TCP or UDP, and creating 65536 unique transports is a high-condition trigger, but the resulting primitive is serious enough to avoid auto-closure.

## 4. Severity interpretation

This is not an ordinary Moderate resource bug. The core issue is integer overflow leading to under-allocation and then a large out-of-bounds write in skb memory. Realistic exploitation evidence for privilege escalation is not demonstrated, so the conservative score stays at Actionable Moderate. The paranoid score reaches Strong Important candidate because kernel OOB write plus possible network-assisted SCTP state creation is a class that requires manual review.

## 5. One-sentence report phrase

An SCTP transport_count integer overflow can cause sock_diag to under-allocate the INET_DIAG_PEERS payload and then copy many peer addresses past the skb tail, resulting in kernel memory corruption and likely DoS with possible higher impact requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. The bug includes an explicitly described skb out-of-bounds write of large size, so it should not be auto-closed even though the trigger conditions are complex.

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

Patch: sctp: prevent peer transport count overflow
Commit: 546221b86ceeba0d8fec92d46a0604bb7b62be07
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=546221b86ceeba0d8fec92d46a0604bb7b62be07

Commit description:

sctp_assoc_add_peer() increments the association's 16-bit transport_count
for every new unique peer. Adding the 65,536th transport wraps the count to
zero.

SCTP sock_diag uses transport_count to reserve the INET_DIAG_PEERS payload,
then copies one sockaddr_storage for every entry in transport_addr_list.
After the wrap, a diagnostic dump reserves an empty payload and writes
8 MiB of peer addresses past the skb tail.

Reject a new unique peer when transport_count has reached U16_MAX. Perform
the check after the existing-peer lookup so a duplicate address continues
to return its existing transport at the limit.

Fixes: 8f840e4 ("sctp: add the sctp_diag.c file")
Cc: stable@vger.kernel.org
Signed-off-by: Asim Viladi Oglu Manizada <manizada@pm.me>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/20260725032053.521705-1-manizada@pm.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sctp/associola.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=546221b86ceeba0d8fec92d46a0604bb7b62be07

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

The original Linux kernel CVE announcement for CVE-2026-74469 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74469

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:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 7

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).