* [CVE-2026-99165][MODERATE REGULAR] sctp: revalidate output stream after association connect wait
@ 2026-10-30 14:57 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-30 14:57 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99165
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: sctp: revalidate output stream after association connect wait
Commit: 77a63d1b813b08c4e5a948f5e04fbaca6176aa8f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77a63d1b813b08c4e5a948f5e04fbaca6176aa8f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99165
Analysis date: Fri, 30 Oct 2026 10:57:01 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A local SCTP sender coordinating stream negotiation with a peer can trigger a NULL-extension dereference and potentially panic hosts configured for fatal oops.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99165 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99165
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 REGULAR
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99165 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99165 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-367;*CWE-20;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'SCTP send processing can retain a stream selection across a connect or send buffer wait that drops the socket lock. Handshake processing or stream reconfiguration can shrink the output stream table and free the selected stream extension before the sender resumes. A later sctp_outq_tail call then dereferences a NULL extension and can cause a kernel oops or a host panic under fatal oops policies. For the CVSS the PR:L value is used because reliable triggering normally requires a local process able to issue the relevant SCTP send operation with a selected stream and coordinate the required association state with a peer. The confirmed primitive is a NULL pointer dereference rather than UAF or arbitrary memory corruption. Confidentiality and integrity impact are therefore N while availability impact is H. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 6.5 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE NULLPTR INIT LEAK UAF NETWORK DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 2.
* Conservative score: 2; no floor or cap applied.
* Raw paranoid score: 2.
* Paranoid score: 2; no technically supported stronger primitive.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Local unprivileged trigger: an ordinary local process can issue the SCTP send with a selected stream; no administrative capability is indicated.
* +1 Reliable kernel crash/strong DoS: the stale stream selection leads to a confirmed NULL-extension dereference; fatal-oops policy can panic the host.
* No additional availability point: panic and oops are the same failure.
* No UAF or corruption point: removed stream extensions are represented by NULL, and the demonstrated access is a NULL-pointer dereference.
* No race penalty: the lock-dropping wait creates a check-to-use window, but the evidence does not establish narrow or unreliable timing.
* No remote-reachability bonus: a peer influences stream negotiation, but a local SCTP sender is also required.
* NEW52/B5-R does not apply: there is no heap OOB write, retry-accumulated index, or later consumption of corrupted written state.
* Controlled reclaim, arbitrary write, disclosure, integrity impact, and authorization bypass are not shown.
3. Reachability analysis
A local non-admin process can select an SCTP output stream and invoke the send path while association establishment or send-buffer waiting drops the socket lock. A cooperating or attacker-controlled peer can reduce the negotiated stream count. No host UID 0, capability, prior privileged setup, special hardware, or namespace-scoped privilege is shown. Triggering requires state coordination, but not a proven hard race.
4. Primitive and severity reading
The exact primitive is a NULL dereference in `sctp_outq_tail()` after the selected stream’s extension was freed during lock release and left NULL. This is invalid active-state consumption, not stale post-lifetime object use, OOB access, or a write primitive. The shown effect is oops/panic availability loss. Non-crash leverage and trust-boundary corruption are unsupported, so this is CLASS_C, not an Important candidate, and automatic Moderate handling remains permissible.
5. One-sentence report phrase
A local SCTP sender coordinating stream negotiation with a peer can trigger a NULL-extension dereference and potentially panic hosts configured for fatal oops.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm product SCTP exposure and fatal-oops policy; no Important-preserving primitive is presently shown.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: sctp: revalidate output stream after association connect wait
Commit: 77a63d1b813b08c4e5a948f5e04fbaca6176aa8f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=77a63d1b813b08c4e5a948f5e04fbaca6176aa8f
Commit description:
When message interleaving is enabled, the first send waits for association
establishment before building its data chunks. The wait drops the socket
lock, and handshake processing can reduce the output stream count to the
peer-advertised inbound stream count. sctp_stream_init() then frees the
extension of every removed stream.
The sender resumes with the stream that it checked before the wait. If the
peer removed that stream, sctp_outq_tail() later dereferences its NULL
extension. Fatal-oops policies then panic the host.
KASAN: null-ptr-deref in range [0x38-0x3f]
RIP: sctp_outq_tail+0x49e/0xaa0
Call Trace:
sctp_primitive_SEND
sctp_sendmsg_to_asoc
sctp_sendmsg
A range check alone is insufficient. Stream reconfiguration can grow the
output count again while the lock is released without recreating extensions
freed by the earlier shrink. The stream can then be in range while its
extension remains NULL. The send-buffer wait has the same issue.
Factor the range and extension checks into a helper and repeat both after
each send-path wait that drops the socket lock. Once the lock is
reacquired, the validation remains stable through data creation and
queueing.
If validation fails after the connect wait, the auto-created association is
already established. Return ESRCH so the existing caller path keeps it
under state-machine ownership instead of freeing it directly, which would
leave protocol, counter and socket state inconsistent.
Fixes: 668c9be ("sctp: implement assign_number for sctp_stream_interleave")
Cc: [email protected]
Assisted-by: LLM
Signed-off-by: Daehyeon Ko <[email protected]>
Acked-by: Xin Long <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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=77a63d1b813b08c4e5a948f5e04fbaca6176aa8f
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99165 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99165
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:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.5
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: unknown
Paranoid ActionableScore: 2
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 REGULAR
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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