[CVE-2026-89479][IMPORTANT] sctp: stop processing a packet once its association is deleted

[CVE-2026-89479][IMPORTANT] sctp: stop processing a packet once its association is deleted

[AL-KERNEL]

CVE: CVE-2026-89479
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: sctp: stop processing a packet once its association is deleted
Commit: ee3f04cf566f6041aa9a0360494fd8db5ade383a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee3f04cf566f6041aa9a0360494fd8db5ade383a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89479
Analysis date: Sat, 12 Sep 2026 06:29:23 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-89479 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89479

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.

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

CVE-2026-89479	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-89479 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-664;CWE-362;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '8.1';DESCR 'A use-after-free can occur in SCTP packet processing when bundled chunks continue to be processed after the association has been deleted. The endpoint receive loop caches chunk asoc and chunk transport without taking a reference, so later chunks in the same packet may write to a freed transport and pass a freed association to the SCTP state machine. For the CVSS the PR:N value is used because a remote SCTP peer can reach this protocol path without local credentials when an SCTP endpoint is exposed. The issue is network reachable and does not require user interaction. Impact is at least remote denial of service via kernel crash and in the worst case may include confidentiality and integrity impact because the primitive is a network reachable use-after-free rather than a simple warning or resource leak. The attack still has high complexity because the vulnerable path depends on specific bundled SCTP chunk state transitions and packet processing from the socket backlog.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7)  SKIP CVE-2026-89479 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	UAF NETWORK LINUS KPANIC PACKET 	-	-	checked

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

ActionableScore=7
ActionableScoreLower=6
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 6
* Conservative score: 6. No floor or cap applied.
* Raw paranoid score: 7
* Paranoid score: 7. No floor or cap applied.
* Final recommended bucket: **Strong Important candidate**::

2. Signal breakdown

Conservative signals:

* +2 Real UAF / active lifetime violation: the association and transport can be freed, while later chunks in the same packet still use cached `chunk->asoc` and `chunk->transport` without holding a reference.
* +2 Remote reachable / directly network-triggerable: a remote SCTP peer can send a crafted bundled SCTP packet to an exposed SCTP endpoint.
* +1 Reliable kernel crash / strong DoS: the stale transport is written through `last_time_heard`, and the freed association is passed to `sctp_do_sm()`, making kernel crash realistic.
* +1 Structured stale-object exploitation leverage: this is not only a stale cleanup dereference. The stale association and transport are active structured networking objects, and the stale association continues into SCTP state-machine processing.

Paranoid additional signal:

* +1 Attacker-influenced active-object lifetime manipulation: the peer controls the packet chunk sequence that creates the association, drives its deletion, and then causes later chunks in the same packet to continue using stale cached references.

Important non-awarded signals:

* Strong Class A exploitation leverage not awarded: no controlled reclaim, arbitrary write, callback control, credential overwrite, or demonstrated LPE is established.
* Concrete repeated release/refcount signal not awarded: the patch establishes post-free write and stale structured use, but not a second `put` or refcount mutation on the exact same dangling reference.
* Extra availability point not awarded: the crash/DoS consequence is already counted once.
* Race/timing penalty not applied: the bug requires a specific packet/state sequence and socket backlog context, but the core issue is a reachable ordered packet-processing lifetime bug, not an externally uncontrollable narrow race.
* Confidentiality and integrity bonuses not awarded separately in ActionableScore: C/I are plausible concerns for manual review because this is network-reachable UAF, but no concrete disclosure or controlled integrity primitive is demonstrated.

3. Reachability analysis

A remote SCTP peer can trigger the vulnerable path when an SCTP endpoint is reachable. No host-admin-equivalent privilege is required on the target, so HostAdminRequired=NO.

The complete trigger is network packet processing, not a namespace-local privileged operation. NamespaceScopedPrivilege=NO.

Prior setup is that the victim has SCTP support and an exposed SCTP endpoint. This is a deployment condition, but it is not a host-admin privilege requirement for the attacker once the endpoint is reachable.

The trigger depends on a specific bundled SCTP chunk sequence that creates an association, caches it, deletes it, and then continues packet processing. The supplied description also notes that the transport is freed through RCU and that the packet must be processed from the socket backlog in task context. This increases exploit complexity, but does not remove remote reachability.

4. Primitive and severity interpretation

The exact primitive is a network-reachable use-after-free of SCTP association and transport objects. The stale transport receives a write to `last_time_heard`, and the stale association is passed into the SCTP state machine.

This is an active structured-object UAF, not fixed stale storage and not a simple cleanup-only fault. There is no concrete repeated release/refcount operation. There is also no demonstrated controlled reclaim or arbitrary kernel read/write.

PrimitiveClass=CLASS_B because a real kernel lifetime/corruption primitive exists and exploitation-leverage analysis is required, but Class A strength is not proven.

Demonstrated consequence is remote kernel crash / DoS. Speculative consequence is broader memory corruption impact or privilege escalation if an attacker can obtain useful reuse or control over the freed objects, but that is not established by the patch alone.

ImportantCandidate=YES because the bug is remotely reachable, involves real post-lifetime use of active structured networking objects, includes a write into freed transport storage, and leaves meaningful exploitation leverage unresolved.

AutoDowngradeAllowed=NO because automatic downgrade would lose a concrete network-reachable kernel UAF with unresolved post-lifetime corruption potential.

5. One-sentence report phrase

A remote SCTP peer can trigger a use-after-free by sending bundled chunks that delete an association while later chunks in the same packet continue using cached association and transport pointers, causing at least kernel crash DoS and requiring manual review for possible stronger memory-corruption impact.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a network-reachable real UAF in SCTP packet processing with a stale write to a freed transport and further stale association use in the state machine.

7. Call-site confidence

Call-site confidence: high

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

Patch: sctp: stop processing a packet once its association is deleted
Commit: ee3f04cf566f6041aa9a0360494fd8db5ade383a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee3f04cf566f6041aa9a0360494fd8db5ade383a

Commit description:

sctp_endpoint_bh_rcv() looks the association up only when chunk->asoc is
NULL, and caches the result in chunk->asoc and chunk->transport without
taking a reference.

A packet that matches no association is handed to the endpoint, so a peer
can bundle COOKIE ECHO, SHUTDOWN and SHUTDOWN ACK in one packet. The
COOKIE ECHO creates the association, the SHUTDOWN chunk caches it, and
with the outqueue empty the SHUTDOWN ACK reaches sctp_sf_do_9_2_final(),
so the association and its transports are freed.

The endpoint loop has no counterpart to the asoc->base.dead check in
sctp_assoc_bh_rcv(). The next chunk writes to last_time_heard in the freed
transport and is then passed to sctp_do_sm() with the freed association.
The transport is freed through RCU, so this needs the packet to come off
the socket backlog, where the loop runs in task context.

The endpoint loop cannot do the same check: it holds no reference on the
association, so reading asoc->base.dead would itself be a use-after-free.
Mark the packet for discard in the command interpreter, just before it
deletes the association. That is also before sctp_inq_free() releases the
chunk on the association receive path.

sctp_sf_do_5_2_4_dupcook() issues SCTP_CMD_DELETE_TCB for the temporary
association, while the one the packet belongs to stays alive. A restarting
peer can bundle DATA behind its COOKIE ECHO, so compare against
chunk->asoc and leave that case alone.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/an-YYtoqw1QpTXUL@v4bel
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sctp/sm_sideeffect.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=ee3f04cf566f6041aa9a0360494fd8db5ade383a

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

The original Linux kernel CVE announcement for CVE-2026-89479 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89479

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:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 8.1

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: 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: 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).