[CVE-2026-68397][IMPORTANT] net/iucv: take a reference on the socket found in afiucv_hs_rcv() [ Upstream

[CVE-2026-68397][IMPORTANT] net/iucv: take a reference on the socket found in afiucv_hs_rcv() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68397
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: net/iucv: take a reference on the socket found in afiucv_hs_rcv() [ Upstream
Commit: 4dc0e63abf8bc7ba8892e617c1fb8b204361e022
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4dc0e63abf8bc7ba8892e617c1fb8b204361e022
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68397
Analysis date: Mon, 10 Aug 2026 20:12:53 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
AF_IUCV HiperSockets receive handling can dereference a freed socket because afiucv_hs_rcv() drops iucv_sk_list.lock without holding a socket reference, allowing a concurrent close to trigger a race-based UAF and likely kernel crash, with paranoid concern for broader memory-corruption impact.

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

The original Linux kernel CVE announcement for CVE-2026-68397 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68397

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-2026-68397	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.1';DESCR 'AF_IUCV HiperSockets receive handling can hit a use after free because afiucv_hs_rcv looks up a destination socket under iucv_sk_list.lock, drops the lock, and then calls callback handlers without holding a socket reference. A concurrent close can free the socket in this window, after which the handler may dereference freed memory such as sk_data_ready(). For the CVSS the PR:L is used because reliable triggering generally requires a local user or process that can create or close AF_IUCV sockets or otherwise control an AF_IUCV endpoint, even though packet delivery enters through the HiperSockets receive path. The issue is network adjacent rather than Internet remote and is mainly relevant to s390 HiperSockets or AF_IUCV deployments. Impact is at least denial of service via kernel crash. In the paranoid score it may include confidentiality and integrity impact because the primitive is a real socket use after free in a receive path, not only a warning or resource leak.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	UAF KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	NO	NO	checked

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

ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. The vulnerable path is a HiperSockets receive path, so another AF_IUCV or HiperSockets peer may influence packet delivery, but this is network-adjacent rather than Internet remote.
* Local unprivileged trigger: +1. Reliable triggering likely needs a local user or process able to create or close AF_IUCV sockets or coordinate an endpoint.
* Generic memory corruption, strong primitive: +2. The bug is a real UAF of a socket object after the list lock is dropped.
* Real lifetime corruption: +1. The patch adds sock_hold() and sock_put(), directly fixing missing lifetime protection.
* Reliable kernel crash / strong DoS: +1. The commit describes dereferencing freed memory, e.g. sk->sk_data_ready().
* Hard or unreliable race / special timing required: -1. Exploitation depends on a concurrent close in a narrow window.
* Rare AND difficult-to-reach subsystem/configuration: -1. AF_IUCV HiperSockets is mainly relevant to s390 environments and is not a broad default Internet-facing stack.

Paranoid additions:

* Weak LPE concern: +1. The stale object is a socket and the dereference reaches callback-style socket operations such as sk_data_ready(), so manual review is justified even without demonstrated reclaim.
* Additional memory-corruption impact concern: +1. In the worst defensible interpretation, socket UAF in a receive path may have confidentiality or integrity implications if reclaim or controlled reuse is possible, but this is not proven by the patch.

Not counted:

* Strong LPE plausibility +2 is not awarded because the patch does not show attacker-controlled reclaim, controlled overwrite, or a demonstrated object replacement primitive.
* Common networking core path +1 is not awarded because this is specialized AF_IUCV / HiperSockets, not a common TCP/IP or netfilter path.

## 3. Reachability analysis

The likely attacker is a local user or local workload that can create and close AF_IUCV sockets while traffic is delivered through the HiperSockets receive path. A peer on the same HiperSockets or AF_IUCV environment may help trigger receive-side processing, but this should be treated as adjacent-network exposure, not public Internet reachability.

Namespaces and containers may matter if AF_IUCV socket access is exposed to reduced-privilege workloads, but this is not a broadly available interface on typical non-s390 systems. The path is specialized and deployment-dependent, which reduces broad exposure, but the lifetime bug itself is concrete.

Call-site confidence: high. The commit explicitly identifies the missing socket reference, the unlock window, the synchronous free path via iucv_sock_kill() -> sock_put(), and a post-free dereference sink.

## 4. Severity interpretation

This behaves stronger than an ordinary Moderate because it is not just a warning or resource leak. It is a race-based UAF in a network receive path.

Realistically, the most likely impact is kernel crash / DoS because the race timing is nontrivial and no controlled reclaim primitive is shown. Paranoid handling should still treat it as an Important candidate for manual review because socket UAF plus callback-style dereference can historically be more dangerous than a plain NULL dereference.

## 5. One-sentence report phrase

AF_IUCV HiperSockets receive handling can dereference a freed socket because afiucv_hs_rcv() drops iucv_sk_list.lock without holding a socket reference, allowing a concurrent close to trigger a race-based UAF and likely kernel crash, with paranoid concern for broader memory-corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a confirmed race-based UAF involving socket lifetime in a receive path, with a callback-style dereference sink. Even though exposure is specialized and exploitation likely requires timing and AF_IUCV/HiperSockets access, the bug class should not be auto-closed.

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

Patch: net/iucv: take a reference on the socket found in afiucv_hs_rcv() [ Upstream
Commit: 4dc0e63abf8bc7ba8892e617c1fb8b204361e022
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4dc0e63abf8bc7ba8892e617c1fb8b204361e022

Changed files:
  net/iucv/af_iucv.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=4dc0e63abf8bc7ba8892e617c1fb8b204361e022

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

The original Linux kernel CVE announcement for CVE-2026-68397 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68397

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:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.1

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: 5
  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).