[CVE-2026-72383][MODERATE 7.0] sctp: fix addr_wq_timer race in sctp_free_addr_wq() [ Upstream

[CVE-2026-72383][MODERATE 7.0] sctp: fix addr_wq_timer race in sctp_free_addr_wq() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72383
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: sctp: fix addr_wq_timer race in sctp_free_addr_wq() [ Upstream
Commit: a8323fb2ab6cd6978f359daeed6688e0cadf32ba
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8323fb2ab6cd6978f359daeed6688e0cadf32ba
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72383
Analysis date: Sun, 16 Aug 2026 04:11:38 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in SCTP address wait queue teardown can allow an in-flight timer callback to access freed per-net SCTP queue memory, causing a kernel use-after-free with realistic local DoS impact and requiring manual review for possible escalation.

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

The original Linux kernel CVE announcement for CVE-2026-72383 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72383

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
======================================================================

CVE-2026-72383	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-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in SCTP addr_wq_timer teardown can leave sctp_addr_wq_timeout_handler running after sctp_free_addr_wq has started freeing addr_waitq entries. Because timer_delete does not wait for an in-flight timer callback to finish, the callback may later take addr_wq_lock and access freed queue memory, resulting in a use-after-free. For the CVSS the PR:L is used because a local user or local process is needed to create the SCTP and namespace teardown conditions in typical deployments. The issue is not directly network reachable because packet traffic alone does not normally free the per-net SCTP address wait queue. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use-after-free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	OOB INIT RACE UAF NETWORK TIMER LINUS  DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative score signals:

* Local unprivileged trigger: +1
  Likely reachable by a local process that can create SCTP state and trigger network namespace or SCTP per-net cleanup. If unprivileged user namespaces are disabled, required privileges may be higher.

* Memory corruption, weak primitive: +1
  This is a race-dependent UAF, but the patch does not show attacker-controlled reclaim, overwrite, type confusion, or controlled stale object reuse.

* Real lifetime corruption: +1
  `timer_delete()` did not wait for an in-flight timer callback, allowing `sctp_addr_wq_timeout_handler()` to access `addr_waitq` after teardown/free.

* Reliable kernel crash / strong DoS: +1
  Accessing freed SCTP queue memory from a timer callback can plausibly lead to an Oops or panic.

* Availability impact realistic: +1
  The impact is host-wide kernel availability, not just a failed operation.

* Hard or unreliable race / special timing required: -1
  The issue depends on a teardown race between the timer callback and `sctp_free_addr_wq()`.

Paranoid adjustment:

* Paranoid score raises the result to 5 because this is a real kernel UAF in a timer callback path.
  However, the race-UAF downgrade rule caps this class at 5 because no concrete reclaim, write-after-free, callback hijack, type confusion, or refcount takeover is shown.

## 3. Reachability analysis

A local process is the realistic trigger. The attacker likely needs to create SCTP-related state and cause teardown of the corresponding per-network-namespace SCTP address wait queue. Namespace behavior matters: if unprivileged user namespaces and network namespaces are enabled, this can be closer to PR:L. If namespace creation is restricted, triggering may require CAP_SYS_ADMIN or equivalent delegation.

The issue is not directly network-triggerable from packet traffic alone. Remote SCTP traffic may influence SCTP state, but the vulnerable free path is a local teardown path, not a normal receive-side protocol parser path.

SCTP is a kernel networking subsystem but not as broadly exposed as TCP, UDP, or netfilter. Realistic exploitation conditions require SCTP availability plus the ability to hit the teardown timing window.

Call-site confidence: medium. The patch shows the unsafe timer teardown site and the commit message explicitly names the racing handler, but the handler body and full call chain are not included.

## 4. Severity interpretation

This behaves like an actionable Moderate kernel lifetime bug. It is more serious than an ordinary DoS-only issue because the primitive is a real use-after-free involving a timer callback and freed queue memory.

Theoretical memory corruption potential exists because stale freed memory is accessed after teardown. Realistic privilege escalation evidence is not demonstrated in the patch: there is no shown attacker-controlled reclaim, controlled overwrite, type confusion, or function pointer control. Therefore it should not be auto-closed, but it is not a strong Important candidate based on the provided evidence alone.

## 5. One-sentence report phrase

A race in SCTP address wait queue teardown can allow an in-flight timer callback to access freed per-net SCTP queue memory, causing a kernel use-after-free with realistic local DoS impact and requiring manual review for possible escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.
YES REQUIRES MANUAL CHECK.

Reason: this is a real kernel UAF race in a timer callback path. Even though no concrete LPE primitive is shown, lifetime bugs of this form should be reviewed manually rather than auto-closed.

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

Patch: sctp: fix addr_wq_timer race in sctp_free_addr_wq() [ Upstream
Commit: a8323fb2ab6cd6978f359daeed6688e0cadf32ba
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a8323fb2ab6cd6978f359daeed6688e0cadf32ba

Changed files:
  net/sctp/protocol.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=a8323fb2ab6cd6978f359daeed6688e0cadf32ba

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

The original Linux kernel CVE announcement for CVE-2026-72383 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72383

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: 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: 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).