[CVE-2026-46227][IMPORTANT] sctp: revalidate list cursor after sctp_sendmsg_to_asoc() in SCTP_SENDALL

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

CVE: CVE-2026-46227
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: sctp: revalidate list cursor after sctp_sendmsg_to_asoc() in SCTP_SENDALL
Commit: 1bfb06ecb00f7fdf35dba8e8f2877346cbe5e078
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1bfb06ecb00f7fdf35dba8e8f2877346cbe5e078
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46227
Analysis date: Mon, 06 Jul 2026 21:00:54 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local unprivileged SCTP user can race SCTP_SENDALL iteration against association peeloff, close, or ABORT processing, leaving a stale list cursor that can cause UAF or type confusion and may allow kernel crash or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-46227 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46227

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-2026-46227	IMPORTANT	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-416;CWE-362;CWE-843;BEST CVSS score: '7';DESCR 'A stale SCTP_SENDALL list cursor can be used after sctp_sendmsg_to_asoc drops the socket lock in sctp_wait_for_sndbuf. While the lock is dropped, another local thread can move or close the cached association, or a network ABORT can free it, leaving the cached tmp cursor stale. This can lead to use-after-free or type confusion when the iterator advances to the cached entry. For the CVSS the PR:L is selected because the trigger is reachable by a local unprivileged process with CapEff 0 through SCTP socket operations, not by a pure remote packet stream alone. The issue is not directly network reachable, although network traffic can participate in one freeing path. Impact is at least local denial of service and may allow privilege escalation because the bug involves UAF or type confusion and a controlled indirect call through outqueue.sched init_sid.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) 	YES	UAF NETWORK LINUS KPANIC 	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:

* **Local unprivileged trigger: +1**. The commit states the paths are reachable from `CapEff=0` via SCTP socket operations.
* **Privilege escalation plausible: +2**. The patch description explicitly mentions type confusion and a controlled indirect call through `outqueue.sched->init_sid`.
* **Memory corruption, strong corruption primitive: +2**. The stale iterator cursor can lead to UAF or type confusion.
* **Real lifetime corruption: +1**. The cached `tmp` can reference an association moved or freed via `kfree_rcu`.
* **Reliable kernel crash / strong DoS: +1**. UAF or invalid list walk can realistically crash the kernel.
* **Hard or unreliable race / special timing required: -1**. The issue depends on a lock-drop window in `sctp_wait_for_sndbuf()` and concurrent peeloff, close, or ABORT processing.

Paranoid additions:

* **Confidentiality impact plausible: +1**. If the controlled indirect call or type confusion is exploitable beyond crash, kernel memory disclosure or privilege-oriented read effects are plausible.
* **Integrity impact plausible: +1**. The described type confusion and indirect call make integrity impact defensible for manual-review triage.

## 3. Reachability analysis

A local unprivileged process can trigger the vulnerable SCTP_SENDALL path by using SCTP socket operations. The issue is not purely remotely reachable, but network traffic can participate because a network ABORT may free the cached association while the socket lock is dropped. Namespaces and containers may matter because SCTP sockets are ordinary kernel networking objects, and a container or reduced-privilege service with access to SCTP may still exercise host kernel SCTP code. Practical exploitation requires SCTP support to be available and the race window to be won, but the commit gives a concrete stale cursor, UAF/type confusion, and indirect-call concern rather than a simple crash-only race.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because it is not just a warning, leak, or validation failure. The realistic baseline is an actionable local kernel DoS with UAF/type confusion. The theoretical but well-supported worst case is local privilege escalation, because the patch context explicitly identifies a type-confusion path with a controlled indirect call target. The race requirement keeps the conservative score below the highest Important range, but the memory lifetime primitive and unprivileged reachability make this unsuitable for auto-close.

## 5. One-sentence report phrase

A local unprivileged SCTP user can race SCTP_SENDALL iteration against association peeloff, close, or ABORT processing, leaving a stale list cursor that can cause UAF or type confusion and may allow kernel crash or privilege escalation.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: the bug has local unprivileged reachability, a real lifetime corruption primitive, explicit UAF/type confusion, and a described controlled indirect call path.

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

Patch: sctp: revalidate list cursor after sctp_sendmsg_to_asoc() in SCTP_SENDALL
Commit: 1bfb06ecb00f7fdf35dba8e8f2877346cbe5e078
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1bfb06ecb00f7fdf35dba8e8f2877346cbe5e078

Commit description:

The SCTP_SENDALL path in sctp_sendmsg() iterates ep->asocs with
list_for_each_entry_safe(), which caches the next entry in @tmp before
the loop body runs.  The body calls sctp_sendmsg_to_asoc(), which may
drop the socket lock inside sctp_wait_for_sndbuf().

While the lock is dropped, another thread can SCTP_SOCKOPT_PEELOFF the
association cached in @tmp , migrating it to a new endpoint via
sctp_sock_migrate() (list_del_init() + list_add_tail() to
newep->asocs), and optionally close the new socket which frees the
association via kfree_rcu().  The cached @tmp can also be freed by a
network ABORT for that association, processed in softirq while the
lock is dropped.

sctp_wait_for_sndbuf() revalidates @asoc (the current entry) on re-lock
via the "sk != asoc->base.sk" and "asoc->base.dead" checks, but nothing
revalidates @tmp .  After a successful return, the iterator advances to
the stale @tmp , yielding either a use-after-free (if the peeled socket
was closed) or a list-walk onto the new endpoint's list head (type
confusion of &newep->asocs as a struct sctp_association *).

Both are reachable from CapEff=0; the type-confusion path gives
controlled indirect call via the outqueue.sched->init_sid pointer.

Fix by re-deriving @tmp from @asoc after sctp_sendmsg_to_asoc()
returns.  @asoc is known to still be on ep->asocs at that point: the
only callers that list_del an association from ep->asocs are
sctp_association_free() (which sets asoc->base.dead) and
sctp_assoc_migrate() (which changes asoc->base.sk), and
sctp_wait_for_sndbuf() checks both under the lock before any
successful return; a tripped check propagates as err < 0 and the loop
bails before the re-derive.

The SCTP_ABORT path in sctp_sendmsg_check_sflags() returns 0 and the
loop hits 'continue' before sctp_sendmsg_to_asoc() is ever called, so
the @tmp cached by list_for_each_entry_safe() still covers the
lock-held free that ba59fb0 ("sctp: walk the list of asoc
safely") was added for.

Fixes: 4910280 ("sctp: add support for snd flag SCTP_SENDALL process in sendmsg")
Cc: stable@vger.kernel.org
Signed-off-by: Ben Morris <bmorris@anthropic.com>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/20260508001455.3137-1-joycathacker@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sctp/socket.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=1bfb06ecb00f7fdf35dba8e8f2877346cbe5e078

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

The original Linux kernel CVE announcement for CVE-2026-46227 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46227

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: Not available
  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: 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).