[CVE-2026-99116][IMPORTANT] net: psp: do not inherit the Rx association on clone

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

CVE: CVE-2026-99116
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: net: psp: do not inherit the Rx association on clone
Commit: a9f14ea73e82db743f0acf4219f499d594589288
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9f14ea73e82db743f0acf4219f499d594589288
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99116
Analysis date: Wed, 28 Oct 2026 22:05:51 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Socket cloning leaves unreferenced PSP association pointers in child/TIME_WAIT sockets, allowing timer cleanup to decrement refcount data after listener closure has freed the association.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-99116 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99116

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
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CVE-2026-99116	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-99116 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC)	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-911;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use after free occurs because sock_copy clones sk psp_assoc into each accepted socket lacking a matching reference, while inet_sock_destruct and later TIME_WAIT cleanup release association related references. After the listener releases the final valid reference, psp_twsk_assoc_free can execute refcount put logic on freed and potentially reused slab memory, with KASAN confirming a 4 byte write after free. For the CVSS the PR:L value is selected because reliable triggering requires local control of PSP association setup and socket state transitions, while a remote peer alone is not shown to create the vulnerable listener state. The confirmed primitive is a constrained UAF write in timer context. It supports kernel crash and makes privilege escalation plausible, but no arbitrary write or proven key disclosure is established. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 6 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to IMPORTANT because the CVSS score, vector or bug class threshold rule was applied. final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_HIGH_BASED_ON_GUESSCVSS and TEMP_KPANIC_MERGE_IMPORTANT_WINS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 4 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	MAYBE	REMOTE INIT LEAK UAF INCREASED_TO_HIGH_BASED_ON_GUESSCVSS TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 5.
* Conservative score: 5; FLOOR 5 applies but does not change the result.
* Raw paranoid score: 6.
* Paranoid score: 6; no cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 real UAF: cloned sockets inherit `psp_assoc` without acquiring references; listener release can free it while TIME_WAIT sockets retain pointers.
* +1 concrete repeated release/refcount mutation: the listener’s final put can end the association lifetime, after which timer cleanup performs another refcount put through a surviving pointer to that same object.
* +1 reliable crash/strong DoS: KASAN confirms a four-byte slab use-after-free write in timer context.
* +1 attacker-influenced lifetime sequence: a socket-controlling actor can drive association acquisition, listening/acceptance, TIME_WAIT creation, and listener closure.
* Paranoid +1: the later operation itself mutates refcount storage after the original object may have been freed, creating a defensible unknown post-free corruption path.
* No arbitrary target, controlled reclaim, callback control, disclosure, or LPE is shown. Structured-leverage and Weak-LPE points are not separately awarded for the same refcount mutation. No extra Availability point is awarded for the same crash.

The first put can free the object; stale TIME_WAIT references survive; the later put is a real lifetime mutation. Therefore the repeated-release +1 and FLOOR 5 apply.

3. Reachability analysis

The grounded trigger is local control of PSP association and socket state transitions; a remote peer alone is not shown to create the vulnerable listener state. Exact PSP setup permissions, UID requirements, capability namespace, and whether an unprivileged or namespace-scoped actor can complete the sequence are not supplied, so host-admin and namespace scope remain unknown. No hard-race penalty applies: this is an ordered socket-lifecycle/refcount sequence, although TIME_WAIT timers delay the final stale mutation.

4. Primitive and severity reading

This is an active association object containing per-connection SPI/key state, but the demonstrated stale use is specifically a timer-time refcount write, not consumption of attacker-shaped key fields. It is stronger than an ordinary cleanup dereference because the second operation actively mutates possibly freed slab storage. That supports CLASS_B, not CLASS_A: the write location and decrement operation are constrained, with no controlled reclaim or directed corruption shown.

ImportantCandidate is YES and auto-downgrade is disallowed because the concrete post-lifetime refcount mutation leaves material exploit leverage unresolved. Likely operational severity is Actionable Moderate pending Important-class exploitability review.

5. One-sentence report phrase

Socket cloning leaves unreferenced PSP association pointers in child/TIME_WAIT sockets, allowing timer cleanup to decrement refcount data after listener closure has freed the association.

6. Manual review advice

MANUAL CHECK REQUIRED

Review reclaim behavior, slab type interactions, trigger privileges, and whether repeated TIME_WAIT callbacks can turn the confirmed stale refcount write into a useful corruption primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: psp: do not inherit the Rx association on clone
Commit: a9f14ea73e82db743f0acf4219f499d594589288
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9f14ea73e82db743f0acf4219f499d594589288

Commit description:

sk->psp_assoc sits past sk_dontcopy_end, so sock_copy() copies it into
every socket accepted from a listener without taking a reference, while
inet_sock_destruct() puts for every inet socket. psp_twsk_init() does
refcount_inc() for the timewait socket, so a child closing through
TIME_WAIT cancels its own put and leaves the association with one
reference and N timewait sockets holding the same pointer. Closing the
listener frees it, and the timewait timers then put freed memory.

Rejecting the association on a listening socket is not sufficient: a socket
can acquire one while established and then be turned back into a listener,
because tcp_disconnect() leaves sk->psp_assoc in place.

  BUG: KASAN: slab-use-after-free in psp_twsk_assoc_free+0x6f/0xf0
  Write of size 4 at addr ffff888110f9255c by task swapper/7/0
   psp_twsk_assoc_free+0x6f/0xf0
   inet_twsk_put+0xda/0x1b0
   call_timer_fn+0x53/0x2e0
   __run_timers+0x764/0xa80
  Freed by task 99:
   kfree+0x1a7/0x500
   process_one_work+0x7ec/0x1100

An association carries a per-connection SPI and key, so a child must not
inherit the parent's. Clear it on clone.

Fixes: 6b46ca2 ("net: psp: add socket security association code")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Reviewed-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/BC10EB92-ABB3-41B2-AB16-266BEEBE18C0@doyensec.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/core/sock.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=a9f14ea73e82db743f0acf4219f499d594589288

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

The original Linux kernel CVE announcement for CVE-2026-99116 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99116

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: 5
  Paranoid ActionableScore: 6

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: NO
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).