[CVE-2026-74752][IMPORTANT] sctp: validate cookie AUTH state before use [ Upstream

[CVE-2026-74752][IMPORTANT] sctp: validate cookie AUTH state before use [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74752
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: sctp: validate cookie AUTH state before use [ Upstream
Commit: 88619b117be1daf633ce32210570ce35a0bd1c98
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=88619b117be1daf633ce32210570ce35a0bd1c98
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74752
Analysis date: Wed, 26 Aug 2026 13:41:35 -0400
ActionableScore: 9
ActionableScore lower bound: 8
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A remote SCTP peer can supply malformed COOKIE_ECHO AUTH state when cookie authentication is disabled, causing OOB reads and a 32-byte OOB write in kernel association handling with DoS and plausible privilege-escalation impact.

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

The original Linux kernel CVE announcement for CVE-2026-74752 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74752

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-2026-74752	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-20;CWE-125;*CWE-787;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '9.8';DESCR 'SCTP cookie AUTH state can be restored from peer controlled cookie bytes when cookie authentication is disabled, but the RANDOM, HMACS, and CHUNKS fields were not validated before association use. A remote peer can supply malformed AUTH parameters that reach later association consumers, causing out of bounds reads during key vector construction and a fixed size write past a zero length AUTH chunk. For the CVSS the PR:N is selected for the paranoid score because triggering does not require an account on the victim when an affected SCTP endpoint is reachable over the network. Impact is at least remote denial of service and in worst case may include confidentiality or integrity impact from kernel memory corruption, so privilege escalation should be considered plausible enough for manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 9)	YES	REMOTE OOB INIT NETWORK LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	NO	NO	checked

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

ActionableScore=9
ActionableScoreLower=8

## 1. ActionableScore

* Conservative score: 8
* Paranoid score: 9
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  SCTP COOKIE_ECHO processing is a network protocol path. A remote SCTP peer can supply the malformed cookie fields if the affected SCTP endpoint is reachable.

* Privilege escalation plausible: +2
  The commit explicitly states that a forged HMAC identifier caused a 32-byte write past a zero-length AUTH chunk and that this provided a primitive for a local privilege escalation chain.

* Memory corruption, strong corruption primitive: +2
  The bug includes both an out-of-bounds read and an out-of-bounds write in kernel SCTP AUTH state handling.

* Reliable kernel crash / strong DoS: +1
  Malformed AUTH cookie state can reach association consumers and corrupt or read outside expected backing arrays, making kernel crash a realistic impact.

* Confidentiality impact plausible: +1
  A forged RANDOM length can cause out-of-bounds reads during key-vector construction.

* Integrity impact plausible: +1
  A 32-byte write past a zero-length AUTH chunk is a concrete kernel memory write primitive.

* Rare / configuration-dependent exposure: -1
  The affected path depends on SCTP AUTH being enabled while cookie authentication is disabled, and on an SCTP endpoint being exposed.

Paranoid delta:

* Availability impact realistic: +1
  For exposed SCTP services, malformed remote COOKIE_ECHO traffic can affect the host kernel network stack and may cause host-wide failure.

## 3. Reachability analysis

The likely trigger is a remote SCTP peer sending a crafted COOKIE_ECHO with malformed AUTH RANDOM, HMACS, or CHUNKS fields. No local account on the victim is required if an affected SCTP endpoint is reachable over the network, so PR:N is reasonable for network-exposed deployments.

The main limiting condition is configuration. The vulnerable path matters when endpoint AUTH is enabled and cookie authentication is disabled. SCTP is less commonly exposed than TCP/UDP services, so exposure is not universal, but this is still a real network protocol receive path rather than a local-only control interface.

Namespaces and containers do not materially reduce concern for the kernel side if the host SCTP endpoint is reachable. If SCTP is only used inside isolated networks, the practical attacker may need internal network access.

## 4. Severity interpretation

This is not an ordinary Moderate issue. The patch and commit describe concrete memory-safety primitives: OOB read and OOB write. The OOB write is especially important because it is in a remotely reachable protocol path and is explicitly linked to an LPE primitive.

Realistic exploitation still depends on SCTP exposure and AUTH configuration, so the conservative score is below automatic Critical handling. However, the combination of remote reachability, concrete kernel memory corruption, and stated privilege-escalation relevance makes this a Strong Important candidate and definitely not suitable for auto-close.

## 5. One-sentence report phrase

A remote SCTP peer can supply malformed COOKIE_ECHO AUTH state when cookie authentication is disabled, causing OOB reads and a 32-byte OOB write in kernel association handling with DoS and plausible privilege-escalation impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: network-reachable kernel memory corruption is present, including a concrete OOB write primitive and an explicit privilege-escalation concern in the patch context.

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

Patch: sctp: validate cookie AUTH state before use [ Upstream
Commit: 88619b117be1daf633ce32210570ce35a0bd1c98
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=88619b117be1daf633ce32210570ce35a0bd1c98

Changed files:
  include/net/sctp/auth.h
  net/sctp/auth.c
  net/sctp/sm_make_chunk.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=88619b117be1daf633ce32210570ce35a0bd1c98

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

The original Linux kernel CVE announcement for CVE-2026-74752 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74752

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:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 9.8

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: 8
  Paranoid ActionableScore: 9

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).